Optoelectronic wiring board, optical communication device, and method of manufacturing the optical communication device

ABSTRACT

An optoelectronic wiring board includes a flex-rigid substrate and an optical communication unit. The flex-rigid substrate includes a flexible substrate provided with an electric wiring, and a pair of rigid sections provided on both sides of the flexible substrate. The pair of rigid sections each include a lamination formed of a conductive circuit and an insulating layer. The optical communication unit is made of a flexible material and has both end faces substantially perpendicular to its optical path of transmitting light. Both end portions of the optical communication unit are disposed and fixed on the rigid sections so that both end faces of the optical communication unit face an optical element mounting region provided on the rigid sections of the flex-rigid substrate.

The present application is a continuation application of Ser. No.12/235,374 filed Sep. 22, 2008, which is now U.S. Pat. No. 7,734,125,patented Jun. 8, 2010, which is a continuation application claimingpriority under 35 U.S.C. §120 to International Application No.PCT/JP2007/055967 filed Mar. 23, 2007, which claims priority to JapanesePatent Application No. 2006-084278 filed Mar. 24, 2006. The contents ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND

The present invention relates to an optoelectronic wiring board, anoptical communication device, and a method of manufacturing the opticalcommunication device, and in particular to a substrate technology forperforming information processing by using a flex rigid substrate.

Conventionally, in electronic equipment such as personal computers,digital video cameras, digital still cameras, CCD modules, liquidcrystal panels, and light-transforming modules, flex rigid substrateshave been used for miniaturization of the equipment.

As flex rigid substrates used in such electronic equipment, various oneshave been proposed (see Japanese laid open publication No. 06-268339,for example).

Furthermore, in electronic equipment as described above, considerableincrease in amount of information to be processed and increase in speedof information processing have been requested with increase inperformance and expansion in functionality.

However, there is a problem that it is difficult for such flex rigidsubstrates to be sufficiently applicable to high-speed processing of alarge amount of information in recent years because elements mounted onthe substrates are operated by electric signals.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, an optoelectronicwiring board includes a flex-rigid substrate and an opticalcommunication unit. The flex-rigid substrate includes a flexiblesubstrate provided with an electric wiring, and a pair of rigid sectionsprovided on both sides of the flexible substrate. The pair of rigidsections each include a lamination formed of a conductive circuit and aninsulating layer. The optical communication unit is made of a flexiblematerial and has both end faces substantially perpendicular to itsoptical path of transmitting light. Both end portions of the opticalcommunication unit are disposed and fixed on the rigid sections so thatboth end faces of the optical communication unit face an optical elementmounting region provided on the rigid sections of the flex-rigidsubstrate.

According to another aspect of the present invention, an opticalcommunication device includes a flex-rigid substrate, an opticalcommunication unit, and a pair of optical elements. The flex-rigidsubstrate includes a flexible substrate provided with an electricwiring, and a pair of rigid sections provided on both sides of theflexible substrate. The pair of rigid sections each include a laminationformed of a conductive circuit and an insulating layer. The opticalcommunication unit is made of a flexible material and has both end facessubstantially perpendicular to its optical path of transmitting light.The pair of optical elements have their respective optical functionalportions that are mounted on the rigid sections of the flex-rigidsubstrate. Both end portions of the optical communication unit aredisposed and fixed on the rigid sections so as to face the opticalelements. A condenser lens is provided on at least one of the end facesof the optical communication unit.

According to still another aspect of the present invention, a method formanufacturing an optical communication device includes preparing aflex-rigid substrate. The flex-rigid substrate includes a flexiblesubstrate provided with an electric wiring, and a pair of rigid sectionsprovided on both sides of the flexible substrate. The pair of rigidsections each include a lamination formed of a conductive circuit and aninsulating layer. A part of an optical communication unit is fixed tothe rigid sections of the flex-rigid substrate with adhesive. Theoptical communication unit is made of a flexible material and has bothend faces substantially perpendicular to its optical path oftransmitting light. A condenser lens is provided on at least one of theend faces of the optical communication unit. The optical elements orsubmount substrates on which the optical element are mounted are mountedon the rigid section of the flex-rigid substrate so that respectiveoptical functional portions of the optical elements are arranged facingthe both end faces of the optical communication unit.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view schematically showing an embodiment ofthe optoelectronic wiring board of the fundamental invention;

FIG. 2A is a cross-sectional view of a flex section of theoptoelectronic wiring board shown in FIG. 1, and FIGS. 2B to 2D arecross-sectional views of a flex section of another embodiment of thefundamental invention;

FIG. 3 is a cross-sectional view schematically showing anotherembodiment of the optoelectronic wiring board of the fundamentalinvention;

FIG. 4A is a cross-sectional view schematically showing anotherembodiment of the optoelectronic wiring board of the fundamentalinvention;

FIG. 4B is a perspective view schematically showing the outline ofanother embodiment of the optoelectronic wiring board of the fundamentalinvention;

FIG. 4C is a cross-sectional view taken along the line A-A′ of FIG. 4B;

FIG. 4D is a cross-sectional view taken along the line B-B′ of FIG. 4B;

FIG. 5 is a cross sectional view schematically showing anotherembodiment of the optoelectronic wiring board of the fundamentalinvention;

FIG. 6 is a cross sectional view schematically showing anotherembodiment of the optoelectronic wiring board of the fundamentalinvention;

FIG. 7 is a cross-sectional view schematically showing an embodiment ofan optical communication device of the fundamental invention;

FIG. 8A is a cross-sectional view schematically showing anotherembodiment of the optical communication device of the fundamentalinvention;

FIG. 8B is a partial cross-sectional view schematically showing anotherembodiment of the optical communication device of the fundamentalinvention;

FIG. 8C is a partial cross-sectional view schematically showing anotherembodiment of the optical communication device of the fundamentalinvention;

FIG. 9 is a cross-sectional view schematically showing anotherembodiment of the optical communication device of the fundamentalinvention;

FIG. 10A is a cross-sectional view schematically showing an embodimentof an optoelectronic wiring board of the present invention, and FIG. 10Bis a cross-sectional view schematically showing another embodiment ofthe optoelectronic wiring board of the present invention;

FIG. 11 is a cross-sectional view schematically showing anotherembodiment of the optoelectronic wiring board of the present invention;

FIGS. 12A and 12B are cross-sectional views schematically showing oneembodiment of an optical communication device of the present invention;

FIG. 13 is a cross-sectional view schematically showing anotherembodiment of the optical communication device of the present invention;

FIGS. 14A to 14C are process diagrams (1) showing an example of a methodfor manufacturing the optoelectronic wiring board according to anembodiment of the present invention;

FIGS. 15A to 15C are process diagrams (2) showing an example of a methodfor manufacturing the optoelectronic wiring board according to anembodiment of the present invention;

FIGS. 16A to 16C are process diagrams (3) showing an example of a methodfor manufacturing the optoelectronic wiring board according to anembodiment of the present invention;

FIGS. 17A to 17B are process diagrams (4) showing an example of a methodfor manufacturing the optoelectronic wiring board according to anembodiment of the present invention;

FIGS. 18A to 18D are process diagrams (5) showing an example of a methodfor manufacturing the optoelectronic wiring board according to anembodiment of the present invention;

FIGS. 19A and 19B are process diagrams (6) showing an example of amethod for manufacturing the optoelectronic wiring board according to anembodiment of the present invention;

FIGS. 20A and 20B are process diagrams showing an example of a methodfor manufacturing the optical communication device according to anembodiment of the present invention;

FIG. 21 is an enlarged cross-sectional view showing the main part ofstill another embodiment of the present invention;

FIGS. 22A and 22B are cross-sectional views showing examples of placeswhere coupling optical waveguides are formed according to an embodimentof the present invention;

FIGS. 23A to 23C schematically illustrate an example of a method forforming a coupling optical waveguide according to an embodiment of thepresent invention;

FIGS. 24A to 24C schematically illustrate another example of a methodfor forming a coupling optical waveguide according to an embodiment ofthe present invention;

FIGS. 25A to 25C schematically illustrate another example of a methodfor forming a coupling optical waveguide according to an embodiment ofthe present invention;

FIGS. 26A to 26C schematically illustrate another example of a methodfor forming a coupling optical waveguide according to an embodiment ofthe present invention;

FIGS. 27A and 27B schematically illustrate another example of a methodfor forming a coupling optical waveguide according to an embodiment ofthe present invention;

FIGS. 28A and 28B schematically illustrate another example of a methodfor forming a coupling optical waveguide according to an embodiment ofthe present invention;

FIGS. 29A and 29B schematically illustrate another example of a methodfor forming a coupling optical waveguide according to an embodiment ofthe present invention; and

FIGS. 30A and 30B schematically illustrate another example of a methodfor forming a coupling optical waveguide according to an embodiment ofthe present invention;

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention will be described below.

Prior to a detailed description of an embodiments of the presentinvention, an embodiment of an invention (referred to as “thefundamental invention” appropriately hereinafter) which becomes apremise of the present invention will be described. In the followingdescription, common terms in the embodiment of the present invention andthe embodiment of the fundamental invention shall have the same meaningsunless otherwise specified, and common parts are referred to as “thepresent invention and the like”.

An optoelectronic wiring board which becomes a premise of the presentinvention is configured in such a manner that rigid sections in which alaminate of conductive circuits and insulating layers has been formed onboth sides of a substrate, and one or more flexible flex sections areintegrated. The optoelectronic wiring board is characterized in thatexternal connection terminals for mounting optical elements and/orpackage substrates on which optical elements are mounted are formed inthe rigid sections and an optical wiring is formed in at least one ofthe flex sections.

The optoelectronic wiring board according to an embodiment of thefundamental invention is configured in such a manner that rigid sectionsand flex sections are integrated. In the rigid sections, externalconnection terminals for mounting optical elements and/or packagesubstrates on which optical elements (also referred to as “opticalelements and the like” simply hereinafter) are mounted are formed, andin at least one of the flex sections, an optical wiring is formed.

In the optoelectronic wiring board according to an embodiment of thefundamental invention having such a configuration, optical wirings areformed in the flex sections and conductive circuits are formed in therigid sections, so that conductive circuits can be formed in portionswhere so high-speed transmission is not required and electric wiringsare sufficient, while only lines which need high-speed transmission canbe optical wirings. As a result, considerable increase in amount ofinformation to be processed and increase in speed of informationprocessing can be achieved without increasing the size of the wiringboard.

In this connection, solder resist layers may be formed in the outermostlayers of the rigid sections as necessary as described later.

Furthermore, the rigid sections and the flex sections are integrated inthe optoelectronic wiring board according to an embodiment of thepresent (fundamental) invention, which means that they are configured soas to be able to transmit optical signals between both of them, andconcrete embodiments of this configuration is not limited in particular.

The optoelectronic wiring board according to an embodiment of thefundamental invention will be described with reference to the figures.

In the following description, when terms are described as superordinateconcepts, the terms are described without a reference numeral even ifthe same words are used.

FIG. 1 is a cross-sectional view schematically showing an embodiment ofthe optoelectronic wiring board of the fundamental invention.

As shown in FIG. 1, this optoelectronic wiring board 100 is composed ofrigid sections 100 a and 100 c in which conductive circuits 125 andinsulating layers 122 are laminated in order on both sides of asubstrate 121, and non-penetrating via holes 127 for connecting theconductive circuits 125 to each other are formed, and a flex section 100b in which a conductive circuit 125 and an optical waveguide 150 areformed on the different sides of the substrate 121, respectively.

The rigid sections 100 a and 100 c and the flex section 100 b areconfigured with one common substrate 121, thereby being integrated.

Furthermore, the optical waveguide 150 is formed on the substrate 121constituting the flex section 100 b and on the substrate 121constituting the rigid sections 100 a and 100 c. The optical waveguide150 is composed of a lower clad 152 a, a core 151, and an upper clad 152b. On the optical waveguide 150, optical path changing mirror 153described later is formed with the inclination of 45 degrees to thesurface being in contact with the optical waveguide of the substrate121.

Furthermore, a conductive circuit 125 is formed on a side of thesubstrate 121 of the flex section 100 b opposite to a side of thesubstrate 121 on which the optical waveguide 150 is formed, and a coverlay 126 is formed on the conductive circuit 125 so as to protect theconductive circuit 125.

In addition, in the rigid sections 100 a and 100 c, optical signalpassing regions 142 a and 142 b are provided which penetrate thesubstrate 121 and the insulating layer 122 on one side of the substrateand solder resist layer 134 on one side of the substrate 121 and arepartially filled with resin composition 147. Respective one ends of theoptical signal passing regions 142 a and 142 b are optically coupledwith the optical waveguide 150.

Specifically, as shown in FIG. 1, the optical waveguide 150 having theoptical path changing mirrors 153 formed directly below the lower endsof the optical signal passing regions 142 a and 142 b is disposed.

Furthermore, external connection terminals 137 for mounting opticalelements and the like are formed on the outermost layer of one side ofeach of the rigid sections 100 a and 100 c.

Furthermore, in the flex section 100 b, the optical waveguide 150 andthe conductive circuit 125 a are formed on the different sides of thesubstrate 121 (see FIGS. 2B to 2D).

In the optoelectronic wiring board 100 configured as mentioned above,one flex section 100 b is formed, and in the flex section 100 b,conductive circuits are formed together with optical wirings.

Thus, in such an optoelectronic wiring board 100, signal transmissionbetween the rigid sections 100 a and 100 c constituting theoptoelectronic wiring board 100 can be performed with optical signals,and electric signals can also be transmitted.

Furthermore, in the optoelectronic wiring board 100, optical signalpassing regions are formed so as to penetrate the substrate and onlypart of the insulating layers constituting the rigid section 100 a and100 c, that is, the substrate 121 and insulating layers 122 laminated onone side of it.

When the optical signal passing regions are formed so as to penetratethe substrate and part of the insulating layers constituting the rigidsections as described above, conductive circuits, non-penetrating viaholes, and the like can be formed freely without making a detour of theoptical signal passing regions in layers where the optical signalpassing regions do not penetrate of the substrate and the insulatinglayers constituting the rigid sections, so that such a configuration issuitable for achieving high density wiring with regard to electricwiring.

Furthermore, when ends of the optical signal passing regions aredirectly coupled optically with optical wirings (here, direct opticalcoupling means a state in which optical signals can be transmittedwithout passing through the insulating layers) as shown in, for example,FIG. 1, the insulating layers need not to be transparent with respect totransmission light, so that the insulating layers can be formed usingcommercial items or the like as used for conventional printed-wiringboards, and optoelectronic wiring substrates can be thus manufactured atlow cost.

FIGS. 2A to 2D are cross-sectional views of the flex section of theoptoelectronic wiring board according to the embodiment of thefundamental invention.

FIG. 2A is a cross-sectional view of the optoelectronic wiring boardshown in FIG. 1. As shown in FIG. 2A, conductive circuits 125 protectedby a cover lay 126 are formed on one side (upper side in the figure) ofthe substrate 121, and an optical waveguide 150 composed of a core 151and a clad 152 is formed on the other side (lower side in the figure)thereof.

The structure of the flex section constituting the optoelectronic wiringboard according to the embodiment of the fundamental invention is notlimited to the one shown in FIG. 2A, and may be the one as shown in FIG.2B, 2C, or 2D, for example.

FIG. 2B, 2C, or 2D is a cross-sectional view schematically showinganother embodiment of the flex section constituting the optoelectronicwiring board according to the embodiment of the fundamental invention.

As shown in FIG. 2B, the flex section according to the embodiment of thefundamental invention may have a structure in which conductive circuits125 functioning as a signal pattern are formed on one side (upper sidein the figure) of the substrate 121, a conductive circuit 125 afunctioning as a ground pattern is formed on the other side (lower sidein the figure), and an optical waveguide 150 composed of a core 151 anda clad 152 is formed on the conductive circuit 125 a. In such a flexsection, the conductive circuits have stripline structures.

On the conductive circuits 125, a cover lay 126 is formed similar to theflex section shown in FIG. 2A.

An example shown in FIG. 2C has a structure in which conductive circuits125 functioning as a signal pattern are formed, and a conductive circuit125 a functioning as a ground pattern is formed via an insulating layer122 on one side (upper side in the figure) of the substrate 121, and aconductive circuit 125 a functioning as a ground pattern is formed onthe other side (lower side in the figure) thereof, and further anoptical waveguide 150 composed of a core 151 and a clad 152 is formed onthe conductive circuit 125 a.

In such a flex section, the conductive circuits have microstripstructures.

On the conductive circuits 125, a cover lay 126 is formed similar to theflex section shown in FIG. 2A.

An example shown in FIG. 2D has a structure in which conductive circuits125 of differential lines 125 b functioning as a signal pattern areformed on one side (upper side in the figure) of the substrate 121, aconductive circuit 125 a functioning as a ground pattern is formed onthe other side (lower side in the figure) thereof, and further anoptical waveguide 150 composed of a core 151 and a clad 152 is formed onthe conductive circuit 125 a. In such a flex section, differentialtransmission of electric signals can be performed.

On the conductive circuits 125, a cover lay 126 is formed similar theflex section shown in FIG. 2A.

Furthermore, the flex section constituting the optoelectronic wiringboard according to the embodiment of the fundamental invention may havea structure in which a power supply pattern is formed instead of aground pattern in a flex section shown in FIGS. 2B to 2D.

Furthermore, the optoelectronic wiring board according to the embodimentof the fundamental invention may have a structure as shown in FIG. 3.FIG. 3 is a cross-sectional view schematically showing anotherembodiment of the optoelectronic wiring board of the fundamentalinvention.

As shown in FIG. 3, this optoelectronic wiring board 200 is constitutedby rigid sections 200 a and 200 c in which conductive circuits 225 andinsulating layers 223 and 222 are laminated in this order on both sidesof a substrate 221, and non-penetrating via holes 227 for connecting theconductive circuits to each other are formed and a flex section 200 b inwhich conductive circuits 225 are formed on both sides of the substrate221.

The rigid sections 200 a and 200 c and the flex section 200 b areconfigured with one common substrate 221, thereby being integrated.

This substrate 221 is composed of an optical waveguide film 250 andresin layers (insulating layers) 221 a provided on both sides thereof.

Since the resin layers 221 a constitute part of optical signal passingregions 242 a and 242 b to be described below, materials having somedegree of transparency for transmission light are used for the resinlayers 221 a. Concrete materials for the resin layers will be describedlater.

In this specification, some degree of transparency for transmissionlight means that the transmission factor for transmission light is60%/30 μm or more at 25° C. In addition, materials having some degree oftransparency for transmission light are also said to be materialstransparent with respect to the transmission light.

On the other hand, the optical waveguide film 250 is composed of a core251 and clads 252. Furthermore, optical path changing mirrors 253 areformed on the optical waveguide 250.

Furthermore, conductive circuits 225 are formed on both sides of thesubstrate 221 in the flex section 200 b, and cover lays 226 are formedon the conductive circuits 225 so as to protect them.

In addition, in the rigid sections 200 a and 200 c, optical signalpassing regions 242 a and 242 b partially filled with resin composition247 are provided which penetrate the insulating layers 223 and 222 onone side of the substrate 221 and a solder resist layer 234 on one sideof the substrate 221. These optical signal passing regions 242 a and 242b are optically coupled with the optical waveguide 250. Specifically, asshown in FIG. 3, the optical path changing mirrors 253 are provideddirectly below the optical signal passing regions 242 a and 242 b.

Furthermore, external connection terminals 237 for mounting opticalelements and the like are formed on the outermost layer of one side ofeach of the rigid sections 200 a and 200 c.

In the optoelectronic wiring board 200 configured as mentioned above,one flex section 200 b is formed, and in the flex section 200 b,conductive circuits are formed together with optical wirings.

Thus, in such an optoelectronic wiring board 200, signal transmissionbetween the rigid sections 200 a and 200 c constituting theoptoelectronic wiring board 200 can be performed with optical signals,and electric signals can also be transmitted when the conductive circuit225 formed in the flex section 200 b is signal pattern.

Although each of the conductive circuits 225 formed in the flex section200 b may be any of a signal pattern, a power supply pattern, and aground pattern, it is desirable that part or all of them be power supplypatterns and/or ground pattern.

When no conductive circuit is formed and only optical wirings are formedin the flex section 200 b, power supply is needed in each of the rigidsections. When the conductive circuit formed in the flex section ispower supply pattern or ground pattern, power may be supplied in one ofthe rigid sections, which provides advantages in miniaturization andhigh density mounting of the optoelectronic wiring board.

Furthermore, in the optoelectronic wiring board 200, optical signalpassing regions 242 a and 242 b are formed so as to penetrate only partof the substrate and insulating layers constituting the rigid sections,that is, part of the substrate 221 and the insulating layers 222 and 223laminated on one side of the substrate 221.

Furthermore, part of the optical signal passing regions 242 a and 242 bis constituted by insulating layers (insulating layers 223 and the like)transparent to transmission light. Such transparent insulating layersmay be formed using materials having excellent transparency fortransmission light (for example, the transmission factor is 90%/mm ormore) and may also be formed using materials having a transmissionfactor of 60%/30 μm or more. Such a material is cheaper and moreadvantageous economically.

Here, an optoelectronic wiring board having one flex section has beendescribed. However, the optoelectronic wiring board according to theembodiment of the fundamental invention may have a plurality of flexsections.

FIG. 4A is a cross-sectional view schematically showing anotherembodiment of the optoelectronic wiring board according to theembodiment of the fundamental invention.

As shown in FIG. 4A, this optoelectronic wiring board 300 includes asubstrate 321 a composed of an optical waveguide film 350 and insulatinglayers 323 formed so as to cover both ends of the optical waveguide film350, a substrate 321 b, on both sides of which conductive circuits 325are formed, insulating layers 323 and 322, and conductive circuits 325.

Furthermore, non-penetrating via holes 327 for connecting conductivecircuits to each other are formed. Portions in which insulating layers322 and 323 are laminated on the substrates 321 a and 321 b constituterigid sections 300 a and 300 c, and a portion in which insulating layers322 and 323 are not laminated constitutes a flex section 300 b. Thesubstrates 321 a and 321 b are components of the rigid sections 300 aand 300 c and the flex section 300 b, and the rigid sections 300 a and300 c and the flex section 300 b are thus integrated.

The substrate 321 a has insulating layers 323 formed so as to cover bothends of the optical waveguide film 350 composed of a core 351 and clads352. Optical path changing mirrors 353 are formed in the opticalwaveguide film 350.

Furthermore, cover lays 326 are formed on the conductive circuits 325 onboth sides of the substrate 321 b so as to protect the conductivecircuits 325.

In addition, in the rigid sections 300 a and 300 c, optical signalpassing regions 342 a and 342 b are formed which penetrate theinsulating layers 323 on one side (upper side in the figure) of thesubstrate 321 a and solder resist layers 334 on one side of thesubstrate 321 a. The optical signal passing regions 342 a and 342 b areoptically coupled with the optical waveguide 350. Specifically, as shownin the figure, the optical path changing mirrors 353 are provideddirectly below the optical signal passing regions 342 a and 342 b.

Furthermore, the optical signal passing regions 342 a and 342 b arepartially filled with resin composition 347.

In the optoelectronic wiring board 300, the optical signal passingregions 342 a and 342 b are formed so as not to penetrate the substrateportion.

Furthermore, external connection terminals 337 for mounting opticalelements and the like are formed on the outermost layer of one side ofeach of the rigid sections 300 a and 300 c.

In the optoelectronic wiring board 300 configured like this, two flexsections are formed. Only optical wirings are formed in one flexsection, and only conductive circuits are formed in the other flexsection.

Thus, in the optoelectronic wiring board 300, signal transmissionbetween the rigid sections 300 a and 300 c constituting theoptoelectronic wiring board 300 can be performed with optical signals,and electric signals can also be transmitted when the conductivecircuits 325 formed in the flex section 300 b are signal patterns.

Although each of the conductive circuits 325 formed in the flex section300 b may be any of a signal pattern, a power supply pattern, and aground pattern, it is desirable that part or all of them be power supplypatterns and/or ground patterns. The reason is as described above.

Furthermore, in the optoelectronic wiring board 300 shown in FIG. 4A, aplurality of flex sections is formed in each of which only eitheroptical wirings or conductive circuits are formed, and the flex sectionsare formed so as to be integrated with different layers of the rigidsections. However, in the embodiment of the fundamental invention, whena plurality of flex sections is formed in each of which only eitheroptical wirings or conductive circuits are formed, the flex sections maybe configured so as to be integrated with the same layer level of therigid sections.

Specifically, the embodiment of the fundamental invention may be anoptoelectronic wiring board having, for example, a form as shown inFIGS. 4B to 4D. FIG. 4B is a perspective view schematically showing theoutline of another embodiment of the optoelectronic wiring board of thefundamental invention. FIG. 4C is a cross-sectional view taken along theline A-A′ of FIG. 4B, and FIG. 4D is a cross-sectional view taken alongthe line B-B′ of FIG. 4B.

As shown in FIGS. 4B to 4D, in this optoelectronic wiring board 900,rigid sections 900 a and 900 c are integrated with a flex section 900 b.In addition, this embodiment has a plurality of flex sections 900 b(1900 a, 1900 b).

In one flex section 1900 a shown in FIG. 4C, an optical waveguide 950 isformed on one side of a substrate 921 a, and a cover lay 926 is formedon a side opposite to a side on which the optical waveguide 950 isformed. In the other flex section 1900 b shown in FIG. 4D, a conductivecircuit 925 is formed on one side of a substrate 921 b, and a cover lay926 for protecting the conductive circuit 925 and a cover lay 926 areformed on both sides of the substrate 921 b. The optical waveguide 950is composed of a core 951 and clads 952, and further optical pathchanging mirrors 953 are formed on the optical waveguide 950.

Conductive circuits 925 and insulating layers 922 are laminated on bothsides of each of the substrates 921 a and 921 b, thereby constitutingthe rigid sections 900 a and 900 c. Furthermore, non-penetrating viaholes 927 for connecting the conductive circuits having insulatinglayers in between are formed.

As mentioned above, the substrates 921 a and 921 b are components of therigid sections 900 a and 900 c and the flex section 900 b, and the rigidsection 900 a and 900 c are integrated with the flex section 900 b.Furthermore, both of the substrates 921 a and 921 b constitute the samelayer of the rigid sections 900 a and 900 c, and each of the flexsections 1900 a and 1900 b are integrated with the rigid sections 900 aand 900 b at the same layer level thereof.

In addition, in the rigid sections 900 a and 900 c, optical signalpassing regions 942 a and 942 b are formed which penetrate theinsulating layers 922 on one side (upper side in the figure) of thesubstrate 921 a and solder resist layers 934 on one side of thesubstrate 921 a (see FIG. 4C). The optical signal passing regions 942 aand 942 b are optically coupled with the optical waveguide 950.Specifically, as shown in FIG. 4C, the optical path changing mirrors 953are provided directly below the optical signal passing regions 942 a and942 b. Furthermore, the optical signal passing regions 942 a and 942 bare partially filled with resin composition 947.

In this optoelectronic wiring board 900, the optical signal passingregions 942 a and 942 b are formed so as not to penetrate the substrate.

Furthermore, external connection terminals 937 for mounting opticalelements and the like are formed on the outermost layer of one side ofeach of the rigid sections 900 a and 900 c.

In the optoelectronic wiring board 900 configured like this, two flexsections are formed. Only optical wirings are formed in one flexsection, and only conductive circuits are formed in the other flexsection. A flex section having optical wirings and a flex section havingconductive circuits are formed in the same layer level.

Thus, in this optoelectronic wiring board 900, signal transmissionbetween the rigid sections 900 a and 900 c constituting theoptoelectronic wiring board 900 can be performed with optical signals,and electric signals can also be transmitted when the conductivecircuits 925 formed in the flex section 900 b are signal patterns.

Although each of the conductive circuits 925 formed in the flex section900 b may be any of a signal pattern, a power supply pattern, and aground pattern, it is desirable that part or all of them be power supplypatterns and/or ground patterns. The reason is as described above.

Furthermore, as is clear from the example shown in FIGS. 4B to 4D, inthe embodiment of the fundamental invention, when a flex section havingoptical wirings and a flex section having conductive circuits are formedin the same layer level, the design flexibility increases.

The reason is that although a layer of rigid sections integrated withflex sections has a tendency that a conductive circuit is difficult tobe formed therein and regions having no conductive circuit and havingonly insulating layers increase therein, if a flex section havingoptical wirings and a flex section having conductive circuits are formedin the same layer level, conductive circuits can be efficiently formedin an insulating layer of another layer.

As shown in FIGS. 4A to 4D, a plurality of flex sections is formed inthe above-described optoelectronic wiring boards 300 and 900, and eitheroptical wirings or conductive circuits are formed in each of the flexsections. However, the optoelectronic wiring board according to theembodiment of the fundamental invention is not always limited to the onein which only either optical wirings or conductive circuits are formedin each of the flex sections, and also in an optoelectronic wiring boardhaving a plurality of flex sections, optical wirings and conductivecircuits may be formed in one of the flex sections similar to theoptoelectronic wiring board 100 shown in FIG. 1, for example.

When only either optical wirings or conductive circuits are formed in aflex section, the thickness of the flex section can be reduced ascompared with a flex section in which both of optical wirings andconductive circuits are formed, and the flex section become easy to bebent so that the flexibility of deformation of the optoelectronic wiringboard for use increases. Furthermore, when only optical wirings areformed in a flex section, no metallic layer which is hard to be bent isformed, and the flex section is made of only resin which is easy to bebent, so that stress concentration caused by a bend is decreased andstress is applied to the whole of the flex section. For this reason,increasing of the optical signal transmission loss caused by a bend canbe prevented. Furthermore, when only conductive circuits are formed in aflex section, the thickness of the flex section can be decreased, sothat the flex section has a tendency that stress concentration causedwhen the flex section is bent, is easy to be decreased.

Furthermore, when only either optical wirings or conductive circuits areformed, the number of processes becomes smaller so that the productionof the flex section becomes easy.

Furthermore, when optical wirings and conductive circuits are formed inthe same flex section, a crack may occur in the optical wirings due tothe difference in thermal expansion coefficients between the opticalwirings and the conductive circuits. However, when only either anoptical wiring or a conductive circuit is formed, it is easy to matchthe thermal expansion coefficients so that no crack occurs and thus itbecomes easy to improve the reliability.

Furthermore, the optoelectronic wiring board according to the embodimentof the fundamental invention may have an embodiment as shown in FIG. 5or FIG. 6.

Each of FIGS. 5 and 6 is a cross sectional view schematically showinganother embodiments of the optoelectronic wiring board according to theembodiment of the fundamental invention.

An optoelectronic wiring board 400 shown in FIG. 5 has substantially thesame configuration as that of the optoelectronic wiring board 200 shownin FIG. 3, and is slightly different therefrom in the configuration ofthe substrate 421 and the configurations of the optical signal passingregions 442 a and 442 b. Because of this, only different points will bedescribed in detail here.

The substrate 421 constituting the optoelectronic wiring board 400 isequivalent to the optoelectronic wiring board in FIG. 3 in thatinsulating layers 423 and conductive circuits 422 are laminated on bothsides of the optical waveguide 450, and is different therefrom in thatno optical path changing mirror is formed on the optical waveguide.

Furthermore, the optical signal passing regions 442 a and 442 b areformed so as to penetrate the whole of the rigid sections 400 a and 400c, and the whole of the optical signal passing regions 442 a and 442 bare constituted by air space.

Furthermore, the optoelectronic wiring board 500 shown in FIG. 6 hassubstantially the same configuration as that of the optoelectronicwiring board 300 shown in FIG. 4A, and is slightly different therefromin the configuration of the substrate 521 a and the configurations ofthe optical signal passing regions 542 a and 542 b. Because of this,only different points will be described in detail here.

The substrate 521 a constituting the optoelectronic wiring board 500 isequivalent to optoelectronic wiring board in FIG. 4A in that insulatinglayers 523 and conductive circuits 522 are laminated on both sides ofthe optical waveguide 550 in the vicinity of both ends of the substrate521 a, and is different therefrom in that no optical path changingmirror is formed on the optical waveguide.

Furthermore, the optical signal passing regions 542 a and 542 b areformed so as to penetrate the whole of the rigid sections 500 a and 500c, and the whole of the optical signal passing regions 542 a and 542 bare constituted by air space.

The optoelectronic wiring boards 400 and 500 configured like this arealso embodiments of an optoelectronic wiring board according to theembodiment of the fundamental invention. When optical elements and thelike are mounted on such optoelectronic wiring boards, optical pathchanging members are provided so as to allow optical signals to betransmitted between the optical elements and the like and the opticalwirings. This will be described in detail later.

In the optoelectronic wiring boards shown in FIGS. 5 and 6, opticalsignal passing regions are formed so as to penetrate all substrates andinsulating layers constituting rigid sections.

In this case, the optical signal passing regions can be formed after allof the insulating layers have been laminated on both sides of thesubstrates (and after solder resist layers have been formed), so thatthe optical signal passing regions can be formed easily.

When such optical signal passing regions is formed, optical pathchanging member is provided as described above. The optical pathchanging member is provided by being fixed with adhesive while beingaligned, and a high accuracy of positioning is not required forpositions where the optical signal passing regions are formed, so thatproducing of the optical signal passing regions is easy.

Furthermore, since the insulating layers do not need to be transparentto transmission light, they can be formed using commercial items and thelike used for conventional printed-wiring boards, so that theoptoelectronic wiring boards can be manufactured at low cost.

In the optoelectronic wiring boards described with reference to thefigures up to this point, optical waveguides are formed as opticalwirings. However, in the optoelectronic wiring board according to theembodiment of the fundamental invention, optical fiber sheets may beformed instead of optical waveguides as optical wirings.

Furthermore, embodiments of the optoelectronic wiring board according tothe embodiment of the present invention are not limited to those shownin the figures, and positions where optical wirings and conductivecircuits are formed are not limited in particular.

Furthermore, in a flex section, optical wirings may be formed on bothsides thereof, may be formed in a multilayer, and may be laminated withconductive circuits.

Furthermore, the number of layers of rigid sections is not limited, andthe rigid sections may be integrated with flex sections at any layers.

Furthermore, in a rigid section according to the embodiment of thepresent invention, a flex substrate constituting a flex section may beformed to be disposed to an end face of the rigid section opposite tothe flex section (see FIG. 10A), or may be formed to be disposedpartially in part of the rigid section (see FIG. 10B).

Next, components of optoelectronic wiring boards according to theembodiment of the present invention and the like will be described.

As optical wirings according to the embodiment of the present inventionand the like, optical waveguides (or optical waveguide films), opticalfiber sheets, and the like can be suitably used.

The optical waveguides include organic optical waveguides made ofpolymer material and the like, because they are excellent inadhesiveness to the insulating layer and are thus easy to be processed.

The polymer material is not limited in particular if it little absorbslight in a communication waveband, and includes thermosetting resin,thermoplastic resin, photosensitive resin, thermosetting resin part ofwhich is made photosensitive, resin complex of thermosetting resin andthermoplastic resin, complex of photosensitive resin and thermoplasticresin, and the like.

Specifically, the polymer material includes polymethyl methacrylate(PMMA), PMMA deuteride, acrylic resin such as deuterium fluorinatedPMMA, polyimide resin such as fluorinated polyimide, epoxy resin, UVcurable epoxy resin, polyolefin resin, silicone resin such as deuteriumsilicone resin, siloxane resin, polymer made of benzocyclobutene, andthe like.

In the embodiment of the present invention and the like, although notlimited particularly, the thickness of the core of an optical waveguideis preferably 1 to 100 μm, and the width thereof is preferably 1 to 100μm. The reason thereof is as follows. If the width of the core of anoptical waveguide is less than 1 μm, formation thereof may be not easy,while if the width thereof is more than 100 μm, it may become a cause ofinhibiting the flexibility of design of conductive circuits and the likeof which constitute the optoelectronic wiring board.

Furthermore, the ratio between the thickness and the width of the coreof an optical waveguide is preferably near 1:1, because the plane shapeof the above light-receiving element and the plane shape of thelight-emitting portion of the above light-emitting element are a circlein general.

The ratio between the thickness and the width of the core of an opticalwaveguide is not limited in particular and only has usually to bebetween about 1:2 and about 2:1.

Furthermore, in the embodiment of the present invention and the like, anoptical waveguide is preferably a multimode optical waveguide. Inparticular, when an optical waveguide is a multimode optical waveguidein the communication wavelength of 0.85 μm, the thickness and width ofits core is more preferably between 20 μm and 80 μm, and is mostpreferably the order of 50 μm.

The reason why a multimode optical waveguide is preferable is that it isrelatively easy to align the optical waveguide with an optical elementand the allowance of the optical waveguide for miss-alignment is large,as compared with a single-mode optical waveguide.

Furthermore, in an optical waveguide according to the embodiment of thepresent invention and the like, particles may be mixed, because a crackis unlikely to occur in the optical waveguide in which particles aremixed. In other words, when any particles are not mixed in an opticalwaveguide, due to differences of the thermal expansion coefficient ofthe optical waveguide from those of other layers (for example,insulating layers and the like), a crack may occur in the opticalwaveguide. While particles are mixed in an optical waveguide to adjustthe thermal expansion coefficient, and thereby differences of thethermal expansion coefficient of the optical waveguide from those ofother layers described above are made small, a crack is unlikely tooccur in the optical waveguide.

Such particles include ones similar to particles contained in resincomposition constituting optical signal passing regions described later,or the like. These particles may be used singly, or two or more kinds ofparticles may be used in combination.

As the particles, inorganic particles are preferable. For example,particles made of silica, titania, or alumina can be suitably used.Furthermore, mixed particles formed by mixing and fusing at least two ofsilica, titania, and alumina can be used.

In addition, in the embodiment of the present invention and the like,shapes of particles are not limited in particular, and includes spheres,ellipsoids, crush shapes, polyhedrons, or the like.

Furthermore, it is desirable that particle diameters of the aboveparticles be smaller (shorter) than the communication wavelength,because if the particle diameters are longer than the communicationwavelength, transmission of an optical signal may be inhibited.

In this case, the particle diameter is length which is the largest sizesof the particles, and it is more desirable that the lower limit of theparticle diameter is 0.01 μm and the upper limit thereof is 0.8 μm. Ifthe particles include ones outside this range, the particle sizedistribution becomes too wide and when the particles are mixed in resincomposition, variations in the viscosity of the resin composition becomelarge, so that the reproducibility of a viscosity in the case ofpreparing the resin composition becomes low, and thereby it may becomedifficult to prepare resin composition having a predetermined viscosity.Furthermore, when the upper limit of the particle diameter is 0.8 μm,the diameters of particles can be smaller than the multimode wavelengthof 0.85 μm and the transmission speed of an optical signal does notincrease.

It is more desirable that the lower limit of the particle diameter is0.1 μm and the upper limit thereof is 0.8 μm. The reason thereof is thatresin composition in which particles in this range are mixed is suitablefor being applied using spin coating, roll coating, or the like, andbecomes easy to be prepared to a predetermined viscosity.

It is most desirable that the lower limit of the particle diameter is0.2 μm and the upper limit thereof is 0.6 μm. Particles in this rangeare particularly suitable for application to esin composition andformation of a core of an optical waveguide. In addition, the variationof an optical waveguide formed, especially the variation of a corebecomes smallest, and resulting in an excellent characteristic of anoptoelectronic wiring board.

Furthermore, the particles may include particles having two or morekinds of different particle diameters provided they have particlediameters in this range.

A desirable lower limit of the amount of the mixed particles is 10weight %, and a more desirable lower limit thereof is 20 weight %. Onthe other hand, a desirable upper limit of the amount of the mixedparticles is 80 weight %, and a more desirable upper limit thereof is 70weight %. The reason thereof is that if the amount of the mixedparticles is less than 10 weight %, the effect of mixing particles maynot be obtained, and if the amount of the mixed particles is more than80 weight %, transmission of an optical signal may be inhibited.

The shape of an optical waveguide described above is not limited inparticular, and it may be shaped as a film because of its easyformation.

When the optical waveguide is composed of a core and a clad, particlesdescribed above may be mixed in both of the core and the clad. However,it is desirable that no particle be mixed in the core and particles bemixed only in the clad with which the core is covered.

The reason thereof is as follows. When particles are mixed in an opticalwaveguide, air gap may be produced at the interfaces between theparticles and the resin component depending on the adhesiveness betweenthe particles and the resin component of the optical waveguide. In thiscase, the directions of refraction of light are changed by the air gap,so that the transmission loss of the optical waveguide may increase. Incontrast to this, when particles are mixed only in the clad, a problemthat the transmission loss of the optical waveguide increases does notarise by mixing particles as described above, and an effect describedabove that a crack is unlikely to occur in the optical waveguide can beobtained.

Furthermore, optical fiber sheets described above include a shape of afilm in which a plurality of optical fibers is arranged in parallel anda periphery thereof is covered with a cover resin layer constituted byresin composition, and the like. In this case, optical fibers may bearranged only in parallel in one layer, or optical fibers arranged inparallel may be stacked in two or more layers.

Such optical fibers, although not limited in particular, include silicaglass optical fibers (SOF), polymerclad optical fiber (POF), hardpolymer clad optical fiber (HPCF), plastic optical fiber, and the like.Among these, silica glass optical fiber (SOF) is preferable because itcan be made small in thickness. Furthermore, when the bending angle of aflex section is small, silica glass optical fiber (SOF) is preferable,and when the bending angle thereof is large, plastic optical fiber (POF)is preferable.

Furthermore, a fiber sheet shaped as a film in which only one opticalfiber is totally covered with resin composition may also be used as theabove fiber sheet.

Furthermore, it is desirable that optical path changing mirror is formedon the optical wiring substrate according to the embodiment of thefundamental invention described above. Because optical paths can bechanged to desirable angles by forming the optical path changingmirrors, thereby being optically coupled with ends of optical signalpassing regions. The optical path changing mirror may come in contactwith air, resin having a different refractive index, or the like, or theoptical path changing mirror may be formed of metal-evaporated layer.The metal-evaporated layer includes a layer made of, for example, gold,silver, platinum, copper, nickel, palladium, aluminum, chrome, alloy ofsome of them, or the like. These materials may be used singly or incombination.

Optical path changing mirror described above may be formed by cuttingoptical wiring and further forming metal-evaporated layer or the like asnecessary. Instead of forming optical path changing mirror on opticalwirings, member having optical path changing portions may be arrangedvia adhesive on tip of end of optical wiring.

When optical path changing mirror described above is formed, angle offormation thereof is not limited in particular and may be selectedappropriately according to optical path. However, optical path changingmirror is generally formed in such a manner that the angle formed withplane which is in contact with insulating layer is 45 or 135 degree. Inthis case, it is preferable to form it at 45 degree from the view pointof easy formation.

In the optoelectronic wiring board according to the embodiment of thefundamental invention, it is desirable that optical signal passingregions be formed. By forming such optical signal passing regions, theflexibility of design of optical wirings is further improved.

The optical signal passing region may be constituted by only air spaces,and part or the whole of it may be filled with resin composition. Whenthe whole of the optical signal passing region is filled with resincomposition, it can be said that the optical signal passing region isconstituted by resin composition.

The resin component of the resin composition is not limited inparticular provided it little absorbs light in a communication waveband,and includes, for example, thermosetting resin, thermoplastic resin,photosensitive resin, thermosetting resin part of which is madephotosensitive, and the like.

Specifically, the resin component includes, for example, epoxy resin, UVcurable epoxy resin, polyolefin resin, polymethyl methacrylate (PMMA),PMMA deuteride, acrylic resin such as deuterium fluorinated PMMA,polyimide resin such as fluorinated polyimide, silicone resin such asdeuterium silicone resin, polymer made of benzocyclobutene, and thelike.

Furthermore, the resin composition may contain particles such as resinparticles, inorganic particles, or metal particles in addition to theresin component as described above. When the resin composition containsthese particles, the optical signal passing regions can be matched inthermal expansion coefficient with the insulating layers and the like,and flame retardancy can be added to the resin composition depending onthe kinds of the particles.

Such particles include, for example, inorganic particles, resinparticles, metal particles, and the like. The inorganic particles aremade of, for example, aluminum compound such as alumina and aluminumhydrooxide, calcium compound such as calcium carbonate and calciumhydroxide, potassium compound such as potassium carbonate, magnesiumcompound such as magnesia, dolomite, basic magnesium carbonate, andtalc, silicon compound such as silica and zeolite, titanium compoundsuch as titania, or the like. Furthermore, the inorganic particles maybe formed by mixing and fusing at least two kinds of inorganicmaterials.

The resin particles include ones made of thermosetting resin,thermoplastic resin, or the like. Specifically, the resin particlesinclude ones made of, for example, amino resin (melamine resin, urearesin, guanamine resin, or the like), epoxy resin, phenolic resin,phenoxy resin, polyimide resin, polyphenylene resin, polyolefin resin,fluoric resin, bismaleimide-triazine resin, or the like.

The metal particles include, for example, gold particles, silverparticles, copper particles, tin particles, zinc particles, stainlesssteel particles, aluminum particles, nickel particles, iron particles,lead particles, and the like. In this case, it is desirable that thesurface of the metal particles be covered with resin or the like inorder to obtain the insulation performance.

These particles may be used singly or in combination of two or morekinds. Furthermore, it is desirable that the shape, maximum length, andamount of particles contained in the resin composition be similar tothose of particles contained in the optical waveguide.

Furthermore, in the optoelectronic wiring board according to theembodiment of the fundamental invention, when the optical signal passingregion is filled with resin composition, it is desirable that thetransmission factor for transmission light of the resin composition be70%/mm or more. Because if the transmission factor is less than 70%/mm,a sufficient ability of optical signal transmission may not be obtained.It is more desirable that the transmission factor be 90%/mm or more.

In this specification, the transmission factor of resin composition is atransmission factor for transmission light per the length of 1 mm. Thetransmission factor is the one measured at room temperature (25° C.).

Furthermore, optical signal passing regions described above may beshaped so as to be able to transmit optical signals through a singlechannel optical wiring, or may be shaped so as to be able to transmitoptical signals through a multichannel optical wiring.

In this case, optical signal passing regions capable of transmittingoptical signals through a multichannel optical wiring may have acollective through-hole structure capable of transmitting opticalsignals of all channels, or may have an individual through-holestructure capable of transmitting an optical signal of each channel. Ineither case, the number of channels is not limited.

Furthermore, in one optoelectronic wiring board, both of optical signalpassing regions having a collective through-hole structure and opticalsignal passing regions having an individual through-hole structure maybe provided.

Optical signal passing regions having the collective through-holestructure may be shaped like, for example, a circular cylinder, a squarepillar, an elliptic cylinder, a shape in which a plurality of circularcylinders is arranged in parallel and sides of circular cylindersadjacent to each other are partially connected to each other, a columnhaving a bottom face surrounded by straight lines and circular arcs, orthe like.

When optical signal passing region is shaped in which a plurality ofcircular cylinders is arranged in parallel and sides of circularcylinders adjacent to each other are partially connected to each other,dummy circular cylinders which do not actually function as opticalsignal passing regions may be partially formed.

Furthermore, it is desirable that each of the vertical sizes and thehorizontal sizes of optical signal passing regions having the collectivethrough-hole structure be between 100 μm and 5 mm, respectively. Whenoptical signal passing regions are shaped as a circular cylinder, it isdesirable that the diameter thereof be in the above range.

When the diameter of the section thereof is less than 100 μm,transmission of an optical signal may be inhibited, while even if it ismore than 5 mm, the transmission loss of an optical signal is notimproved, and miniaturization of the optoelectronic wiring board thusbecomes difficult.

Furthermore, optical signal passing regions having the individualthrough-hole structure may be shaped like, for example, a circularcylinder, a square pillar, an elliptic cylinder, a column having abottom face surrounded by straight lines and circular arcs, or the like.

It is desirable that the lower limit of the diameter of the section ofeach of the optical signal passing regions having an individualthrough-hole structure be 100 μm and the upper limit thereof be 500 μm.When the diameter is less than 100 μm, an optical path may be blocked,and it may be difficult to fill the optical signal passing regions withuncured resin composition. On the other hand, even if the diameter ismore than 500 μm, the optical signal transmittance is not so improved,which may become a cause of inhibiting the flexibility of design ofconductive circuits and the like constituting the optoelectronic wiringboard.

A more desirable lower limit of the diameter is 250 μm and a moredesirable upper diameter thereof is 350 μm.

In the embodiment of the fundamental invention, the sectional diameterof a portion of an optical signal passing region penetrating substratesand insulating layers is, when the optical signal passing region isshaped as a circular cylinder, the diameter of the section thereof, whenit is shaped as an elliptic cylinder, the longitudinal diameter of thesection thereof, or when it is shaped as a square column or a polygonalcolumn, the length of the longest portion of the section thereof.Furthermore, in the embodiment of the fundamental invention, the sectionface of an optical signal passing region is a section parallel to theprincipal plane of a rigid section of the optoelectronic wiring board.

It is desirable that the optical signal passing region be formed in asize that transmission light is not reflected by the wall surfacethereof at optical signal transmission, because there is not a fear thatoptical signal transmission is affected by roughness of the wall surfaceof the optical signal passing region.

Furthermore, in order that an optical signal passing region is formed ina size that transmission light is not reflected by the wall surface, itis desirable to design so that collimated light transmit inside theoptical signal passing region by disposing a microlens described later.

The wall surface of an optical signal passing region may be constitutedby resin or metal. Since an insulating layer is usually exposed at thewall surface of an optical signal passing region, it can be said thatthe wall surface is constituted by material similar to that of theinsulating layer. Thus, when the insulating layer is made of resin, itcan be said that the wall surface of the optical signal passing regionis constituted by resin even if it is not treated in particular.

However, a resin layer may be formed on the wall surface of the opticalsignal passing region separately. In this case, it is desirable that theresin layer be configured so as to function as a clad, and resincomposition filled inside the optical signal passing region beconfigured so as to function as a core.

When the wall surface of an optical signal passing region is constitutedby metal, as the material thereof, for example, copper, nickel, chrome,titanium, noble metal, or the like may be suitably used.

Furthermore, when a metallic layer is formed on the wall surface of anoptical signal passing region, the metallic layer may be formed in onelayer or in two or more layers.

Such a metallic layer is able to, in some cases, serve as athrough-hole, that is, serve to electrically connect between conductivecircuits of which a substrate is sandwiched, or between conductivecircuits of which a substrate and an insulating layer are sandwiched.

When a resin layer or a metal layer is formed on the wall surface of theoptical signal passing region, it is desirable that the surface (whichis in contact with resin composition filled inside) be a rough surfacehaving surface roughness between 0.1 μm and 5 μm, because theadhesiveness of the surface to the resin composition is improved.

The rough surface may be formed by etching or the like.

Furthermore, in the optoelectronic wiring board according to theembodiment of the fundamental invention, the shapes, forming positions,and the number of the optical signal passing regions are not limited inparticular, and may be selected appropriately in consideration of thedesign of the optoelectronic wiring board, that is, in consideration offorming positions of external connection terminals and forming positionsand the like of optical waveguides and conductive circuits.

However, it is desirable that the above-described optical signal passingregion is formed so as to penetrate the insulating layer of oneoutermost layer, and conductive circuit and/or pad is formed on an outerlayer side of the insulating layer of the other outermost layer and inposition on extension line of the side of the optical signal passingregion optically coupled with optical wiring.

With such a configuration, high density wiring of optical wirings andconductive circuits can be performed and high density mounting ofoptical elements and various kinds of electronic components can beperformed.

Here, such pads are provided to mount optical elements and various kindsof electronic components.

In the optoelectronic wiring board according to the embodiment of thefundamental invention, when an optical signal passing region is formed,a microlens may be provided on the end and the like of a side oppositeto a side optically coupled with an optical wiring of the optical signalpassing region. In this case, the microlens may be arranged directly orvia optical adhesive.

By arranging a microlens, an optical signal is focused by the microlens,thus being transmitted more reliably.

A microlens used in the embodiment of the fundamental invention is notlimited in particular and includes one used in an optical lens, andconcrete material thereof includes optical glass, resin for opticallens, or the like. Resin for optical lens includes material similar topolymer material described as resin composition, such as acrylic resinor epoxy resin, filled in the optical signal passing regions.

Furthermore, a shape of the microlens is, for example, a convex lenshaving a convex surface on one side thereof, or the like. The radius ofcurvature of the convex surface of the lens may be selectedappropriately in consideration of the design of the optical signalpassing region and the like. Specifically, for example, when the focaldistance needs to be increased, it is desirable to increase the radiusof curvature, and when the focal distance needs to be shortened, it isdesirable to reduce the radius of curvature.

The shape of the microlens is not limited to a convex lens, and may havea shape that has only to be able to focus an optical signal in a desireddirection.

It is desirable that a microlens used in the embodiment of the presentinvention and the like have a transmission factor of 70%/mm or more forcommunication wavelength light, because if the microlens has atransmission factor less than 70%/mm for communication wavelength light,the loss of an optical signal is large and the optical signaltransmittance may be thus reduced. In addition, it is more desirablethat the transmission factor be 90%/mm or more.

Such a microlens is usually applied and formed using an inkjet device, adispenser, or the like.

A desirable lower limit of the mixed amount of particles in themicrolens is 5 weight %, and a more desirable lower limit thereof is 10weight %. On the other hand, a desirable upper limit of the mixed amountof the particles is 60 weight %, and a more desirable upper limitthereof is 50 weight %. The reason thereof is that if the mixed amountof particles is less than 5 weight %, the effect of mixing particles maynot be obtained, and if the mixed amount of particles is more than 60weight %, transmission of an optical signal may be inhibited.

Furthermore, when the optoelectronic wiring board according to theembodiment of the present invention and the like has multichanneloptical wirings and microlenses are arranged on the optoelectronicwiring board, the microlenses may be independent of one another, or maybe a microlens array in which a plurality of lenses is arranged inparallel.

Furthermore, when the microlenses are arranged, it is desirable that amicrolense arranged on a side facing a light-emitting element bedesigned so as to be focused to a core of an optical waveguide on a sideopposite to a side facing the light-emitting element, and a microlensarranged on a side facing a light-receiving element be designed so as tochange light transmitted from the optical waveguide to be collimatedlight.

As mentioned above, the microlenses may be arranged directly or viaoptical adhesive, and it is more preferable that they be arrangeddirectly.

The optical adhesive used is not limited in particular, and may be epoxyresin system, acrylic resin system, silicone resin system, and the like.

Furthermore, it is desirable that the optical adhesive have a viscositybetween 0.2 Pa·s and 1.0 Pa·s, a refractive index between 1.4 and 1.6,an optical transmission factor of 80%/mm or more, and a coefficient ofthermal expansion (CTE) between 4.0×10⁻⁵/° C. and 9.0×10⁻⁵/° C.

Concrete optical adhesive includes, for example, Optodyne UV-4000 ofDaikin Industries, Ltd, adhesive for optical path coupling (having arefractive index between 1.46 and 1.57) of NTT Advanced TechnologyCorporation, or the like.

Furthermore, it is desirable that the thickness of the optical adhesiveis 50 μm or less.

Furthermore, when the microlens is arranged, surface treatment may havebeen made on regions where it is arranged.

The reason thereof is as follows. When resin for forming a microlens isapplied by an inkjet device or the like, variations in the shape,especially the sag height, of the microlens are easy to occur due to thedispersion in process conditions before forming a solder resist layerand/or wettability of a portion where the microlens is arranged causedby the time of standing. In contrast to this, variations in the sagheight of the microlens can be reduced by performing surface treatmentand the like by water-repellent coating agent.

Such surface treatment includes, for example, treatment bywater-repellent coating agent such as fluorinated polymer coating agent(having a surface tension between 10 mN/m and 12 mN/m), water-repellenttreatment by DF4 plasma, hydrophillic treatment by O2 plasma, and thelike.

Furthermore, a microlens described above may be arranged via a lensmarker.

As such a lens marker, for example, the one disclosed in Japanese PatentApplication Laid-open No. 2002-331532 or the like may be suitably used.

When a lens marker has been formed, it is desirable that the microlensbe arranged on the lens marker subjected to water-repellent treatment orhydrophilic treatment.

When the surface of the lens marker is stained, there is a case thatresin composition used for forming a microlens (resin composition forlens) is not spread uniformly and may thus become a cause of beingincapable of forming a microlens having a desired shape. However, byperforming the water-repellent treatment or the hydrophilic treatment,dirt of the surface of the lens marker can be removed, and the resincomposition for lens can be spread uniformly on the lens marker.

In addition, it is more desirable that the lens marker be subjected tohydrophilic treatment than to water-repellent treatment.

When the lens marker is subjected to hydrophilic treatment, resincomposition for lens dropped for arranging the microlens on the lensmarker is likely to spread on the whole of the lens marker, and spreadof the resin is sure to be stopped at the outer periphery of the lensmarker, so that hydrophilic treatment is suitable to form a microlenshaving a predetermined shape by surface tension.

A microlens having a configuration similar to that of a microlensdescribed above may also be used in the present invention describedlater.

Next, the optical communication device according to the embodiment ofthe fundamental invention will be described.

The optical communication device according to the embodiment of thefundamental invention is characterized in that the above-describedoptoelectronic wiring board according to the embodiment of thefundamental invention having optical element and/or a package substrateon which optical element is mounted on a motherboard.

In the optical communication device according to the embodiment of thefundamental invention, optical wirings are formed in the flex sectionsand conductive circuits are formed in the rigid sections, so thatconductive circuits can be formed in portions where so high-speedtransmission is not required and electric wirings are sufficient, whileonly lines which need high-speed transmission can be optical wirings. Asa result, considerable increase in amount of information to be processedand increase in speed of information processing can be achieved withoutincreasing the size of the wiring board.

Specifically, for example, when the optical communication device is usedin a mobile phone, in image transmission, RGB signals can be transmittedwith optical wirings because high-speed processing is desired, whilesignals for adjusting the contrast, brightness, of the screen and thelike can be transmitted with electric wirings (conductive circuits)because high-speed processing is not particularly required.

In other words, in the optical communication device according to theembodiment of the fundamental invention, signals which need high-speedprocessing can be transmitted at high speed with optical wirings, andsignals, power supplies, and grounds which do not need high-speedprocessing can be transmitted at low speed with electric wirings(conductive circuits).

Such an optical communication device may be used in not only a mobilephone but also various devices such as a personal computer, a digitalvideo camera, digital camera, a CCD module, a liquid crystal panel, anda light-transforming module, and its application is not limited.

The optoelectronic wiring board and the optical communication deviceaccording to the embodiment of the present invention can be usedeffectively for signal transmission between a control section and ascreen section of a mobile phone, a personal computer, a digital camera,or the like, signal transmission in a substrate between a CPU and amemory or the like, and signal transmission for substrates between amotherboard and a backplane board or the like, and thereforeconsiderable increase in amount of information to be processed andincrease in speed of information processing can be achieved usingoptical transmission.

Embodiments of the optical communication device according to theembodiment of the fundamental invention will be described with referenceto the figures.

FIG. 7 is a cross-sectional view schematically showing an embodiment ofthe optical communication device according to the embodiment of thefundamental invention.

In the optical communication device 600 shown in FIG. 7, alight-receiving element 139 and a light-emitting element 138 are mountedon the optoelectronic wiring board 100 shown in FIG. 1 via solderconnecting portions. The optical communication device 600 is configuredsuch that an optical signal output from the light-emitting element 138is transmitted to the light-receiving element 139 through an opticalsignal passing region 142 b, an optical waveguide 150, and an opticalsignal passing region 142 a.

Furthermore, when an optical wiring and a conductive circuit are formedin a flex section 100 b of the optical communication device 600 as shownin FIG. 7, the whole of the optical communication device can be driveneven if the optical communication device 600 is not connected with amotherboard substrate or the like.

On the optical communication device according to the embodiment of thefundamental invention or the optical communication device according tothe embodiment of the present invention described later, opticalelements such as a light-receiving element, a light-emitting element,and the like are mounted. These may be used properly as appropriate inconsideration of the configuration, the required characteristic, and thelike of a package substrate described above. The light-receiving elementincludes, for example, a photodiode (PD), an avalanche photodiode (APD),or the like.

The material of the light-receiving element includes Si, Ge, InGaAs, orthe like. InGaAs is most desirable in these materials because of theexcellent light-receiving sensitivity.

On the other hand, the light-emitting element includes, for example, anLD (semiconductor laser), a DFB-LD (distributed feedback semiconductorlaser), an LED (light-emitting diode), an Infrastructure oroxide-confined VCSEL (vertical cavity surface-emitting semiconductorlaser), or the like.

These may be used properly as appropriate in consideration of theconfiguration, required characteristic, and the like of the opticalcommunication device.

The material of the light-emitting element includes a compound ofgallium, arsenic and phosphorus (GaAsP), a compound of gallium,aluminum, and arsenic (GaAlAs), a compound of gallium and arsenic(GaAs), a compound of indium, gallium, and arsenic (InGaAs), a compoundof indium, gallium, arsenic, and phosphorus (InGaAsP), or the like.

Furthermore, an optical element such as a light-receiving element, alight-emitting element, or the like may be a multichannel opticalelement, and the number of channels thereof is but not limited to 4ch,8ch, 12ch, or the like, and the pitch is but not limited to 125 μm, 250μm, 500 μm, or the like.

When an optical element is an array element having a multichannel, thelight-receiving portion or the light-emitting portion thereof may bearranged on a straight line, or may be arranged in two dimensions.

The optical element may be mounted by flip chip bonding or wire bonding.

Furthermore, a micro lens described above may be provided on thelight-receiving face of the light-receiving element or thelight-emitting face of the light-emitting element.

The optical elements may be mounted in a state being mounted on apackage substrate.

When the optical element or the package substrate on which the opticalelement is mounted, is mounted, an underfill may be filled therein afterthe mounting.

In this case, an underfill material is not limited in particular, andfor example, may use thermosetting resin, luminescent resin, resin inwhich a photosensitive group is added to part of thermosetting resin,resin complex including these resins and thermo plastic resin, or thelike. Furthermore, commercial underfill resin may also be used.

It is desirable that the underfill have a transmission factor of 70%/mmor more for communication wavelength light. Because if the underfill hasa transmission factor less than 70%/mm for communication wavelengthlight, the loss of an optical signal is large and the optical signaltransmittance may be thus reduced. In addition, it is more desirablethat the transmission factor be 90%/mm or more. Incidentally, theunderfill may be filled only in portions other than the portionsconstituting the optical path. In this case, the transmission factor ofthe underfill is not limited in particular.

The above-described thermosetting resin includes, for example, epoxyresin, phenol resin, polyimide resin, polyester resin, bismaleimideresin, polyolefin resin, polyphenylene ether resin, polyphenylene resin,fluororesin, or the like.

The photosensitive resin includes, for example, acrylic resin, or thelike.

Furthermore, the resin in which a photosensitive group is added to partof thermosetting resin, includes, for example, resin obtained by acrylicreaction between the thermoset group of the thermosetting resin andmethacrylic acid or acrylic acid, or the like.

Furthermore, the thermoplastic resin includes, for example, phenoxyresin, polyeter sulfone (PES), polysulfone (PSF), polyphenylene sulfone(PPS), polyphenylene sulfide (PPES), polyphenylene ether (PPE),polyeter-imide (PI), or the like.

Furthermore, the underfill may contain particles when the underfillcontains particles, the coefficient of thermal expansion can be adjustedby the mixed amount thereof, the coefficient of thermal expansion can bematched between the underfill and the package substrate or the opticalelement.

A concrete example of such particles includes particles similar to thosecontained in the optical signal passing regions described above.

Furthermore, when such particles are contained in the underfill, it isdesirable that the lower limit of the mixed amount of the particles be20 weight % and the upper limit thereof be 70 weight %. Because if themixed amount is generally in this range, it is suitable for matching thecoefficient of thermal expansion of the underfill to that of the packagesubstrate or the optical elements, and the underfill has fluidityrequired at filling.

A more desirable lower limit is 30 weight %, and a more desirable upperlimit is 60 weight %.

In the optical communication device according to the embodiment of thefundamental invention, optical path changing members may be provided onthe optoelectronic wiring board. In this case, it is desirable that theoptical path changing member is provided being fixed to the opticalelement, or provided via a submount substrate.

Concrete examples of an optical communication device on which theoptical path changing members are provided will be described withreference to FIGS. 8A, 8B, 8C, and 9.

FIG. 8A is a cross-sectional view schematically showing an embodiment ofthe optical communication device according to the embodiment of thefundamental invention, and FIGS. 8B and 8C are partial cross-sectionalviews schematically showing an embodiment of the optical communicationdevice according to the embodiment of the fundamental invention.

In the optical communication device 700 shown in FIG. 8A, alight-receiving element 439 and a light-emitting element 438 are mountedon the optical communication device 400 shown in FIG. 5 via solderconnecting portions, and optical path changing members 462 are provided.

The optical path changing members 462 are fixed to the optical elements(light-receiving element 439 and light-emitting element 438) via opticaladhesive 461 transparent to transmission light. In addition, opticalpath changing minors 463 are formed on sides opposite to sides fixed tothe optical elements of the optical path changing members 462.

The optical communication device 700 is configured such that an opticalsignal output from the light-emitting element 438 is transmitted to thelight-receiving element 439 through an optical signal passing region 442b (optical path changing member 462), an optical waveguide 450, and anoptical signal passing region 442 a (optical path changing member 462).

Portions of the optical path changing members 462 inserted in theoptoelectronic wiring board may be fixed to the wall surfaces of theoptical signal passing regions via adhesive.

The materials of the optical path changing members include, for example,those similar to the material of the optical waveguide, or the like asmentioned above. Furthermore, an optical waveguide film or an opticalfiber sheet having an optical path changing mirror formed on an endthereof may be used as an optical path changing member.

Furthermore, when the mounted optical elements are multichannel opticalelements, the optical path changing members may be sized to be able tochange optical paths of optical signals of all channels, or an opticalpath changing member may be provided for each of the channels.

Furthermore, the optical adhesive includes adhesive similar to theoptical adhesive used when a microlens described above is provided, orthe like.

Furthermore, when optical path changing member is provided in theoptical communication device according to the embodiment of thefundamental invention, it may be provided via submount substrate asshown in FIGS. 8B and 8C.

For example, in an example shown in FIG. 8B, a submount substrate 471 isfixed on a solder resist layer 434 via adhesive 475, and alight-receiving element 439 is mounted on the submount substrate 471 bysolder 473 via pads 472 formed on the submount substrate 471. The pads472 are connected with conductive circuits 425 of the optoelectronicwiring board by bonding wires 474. Furthermore, an optical paththrough-hole 471 a is formed in the submount substrate 471. On the sideof the submount substrate 471 opposite to the side on which alight-receiving element 439 is mounted, an optical path changing member462 on which an optical path changing mirror 463 is formed is fixed viaoptical adhesive 461.

Furthermore, the submount substrate 471, the light-receiving element439, and the bonding wires 474 are covered and sealed with resinmaterial 478 transparent to transmission light. As described above, inthe optical communication device according to the embodiment of thefundamental invention, an optical path changing member may be providedvia a submount substrate.

A portion inserted in the optoelectronic wiring board of the opticalpath changing member 462 may be fixed to the wall surface of the opticalsignal passing region via adhesive.

In an example shown in FIG. 8C, a submount substrate 471 is placed on asolder resist layer 434, and a light-receiving element 439 is mounted bysolder 473 via pads 472 formed on the submount substrate 471. The pads472 are extended to sides of the submount substrate 471, and the pads onthe sides are connected to conductive circuits 425 of the optoelectronicwiring board by solder 476. The submount substrate itself is also fixedby the solder 476.

Furthermore, an optical path through-hole 471 a is formed in thesubmount substrates 471. On the side of the submount substrate 471opposite to the side on which a light-receiving element 439 is mounted,an optical path changing member 462 on which an optical path changingmirror 463 is formed, is fixed via optical adhesive 461.

In the embodiment of the fundamental invention, the submount substrateis not limited in particular, and includes, for example, a glasssubstrate, a ceramic substrate, a resin substrate, or the like.

Although an optical path through-hole is formed in the submountsubstrate shown in the figure, if the submount substrate itself istransparent to transmission light, this optical path through-hole is notnecessary to be formed. Furthermore, the optical path through-hole maybe filled with resin composition.

Furthermore, conductivity between the optical element and theoptoelectronic wiring board is provided by wire bonding in FIG. 8B or bysoldering made on the sides of the submount substrate in FIG. 8C, butmay be provided in such a way that a pad which is connected to a pad formounting the optical element via the through-hole is previously formedon a side of the submount substrate opposite to a side on which theoptical element is mounted before the submount substrate is mounted onthe optoelectronic wiring board, and then the submount substrate isconnected to the optoelectronic wiring board by solder using a solderingtechnology such as a BGA or a CSP.

The optical communication device according to the embodiment of thefundamental invention may be an embodiment as shown in FIG. 9.

FIG. 9 is a cross-sectional view schematically showing an embodiment ofthe optical communication device according to the embodiment of thefundamental invention.

In the optical communication device 800 shown in FIG. 9, alight-receiving element 539 and a light-emitting element 538 are mountedon the optical communication device 500 shown in FIG. 6 via solderconnecting portions, and optical path changing members 562 are provided.

The optical path changing members 562 are fixed to the optical elements(light-receiving element 539 and light-emitting element 538) via opticaladhesive 561 transparent to transmission light. In addition, opticalpath changing minors 563 are formed on sides of the optical pathchanging members 562 opposite to the sides fixed to the opticalelements.

In the optical communication device 800, an optical signal emitted fromthe light-emitting element 538 is transmitted to the light-receivingelement 539 through an optical signal passing region 542 b (optical pathchanging member 562), an optical waveguide 550, and an optical signalpassing region 542 a (optical path changing member 562).

Portions of the optical path changing members 562 inserted in theoptoelectronic wiring board may be fixed to the wall surfaces of theoptical signal passing regions via adhesive, or may be fixed by adhesivefilling the whole of the optical signal passing regions in which theoptical path changing members have been inserted.

An optical communication device having optical path changing members hasbeen depicted in FIGS. 8A to 8C or FIG. 9. An optical path changingmember of the optical communication device according to the embodimentof the fundamental invention may be provided, for example, in such amanner that the wall surface of a portion in which the optical pathchanging member is inserted in the optoelectronic wiring board is alsofixed to the wall surface of an optical signal passing region viaadhesive, except a manner already described.

However, rather than being provided in such a manner, an optical pathchanging member is preferably provided so as to be fixed to an opticalelement or provided via a submount substrate as described above, becausewhen an optical path changing member is provided in such a manner thatit is inserted in an optoelectronic wiring board and the wall surfacethereof is fixed with adhesive, the optical path changing member needsto be fixed while being aligned by active alignment, but when an opticalpath changing member is provided being fixed to an optical element orvia a submount substrate, it can be aligned by passive alignment, sothat it is relatively easy to align the optical axis thereof.

Furthermore, a convex lens or a diffraction grating lens may be formedon the reflecting surface of the optical path changing member, and aconvex lens may be provided on a side (a side in optical contact with anoptical wiring) of the optical path changing member.

Furthermore, when an optical path changing member is provided in theoptical communication device according to the embodiment of thefundamental invention, the optical path changing member may be fixed toan optical signal passing region of the package substrate describedabove.

Next, the features according to the embodiment of the present inventionwill be described in detail.

In the embodiment of the fundamental invention described above, anoptical wiring substrate and optical communication devices aremanufactured by an existing printed substrate process. However, such aprinted substrate process is almost a plane process, and it is verydifficult to make an optical path changing mirror having a 45-degreesurface (see FIG. 7, for example) which satisfies the positionalaccuracy, the mirror evenness, the mirror angle accuracy, and thepossibility of forming a selective reflecting metal surface by anexisting printed substrate process.

Furthermore, also in a method of making a component having a 45-degreesurface mirror (for example, an optical path changing portion 462) andinserting the component in a hole of a substrate as shown in FIG. 8B or8C, it is very difficult at the present time to insert the component inthe hole and fixing it to the hole while keeping a positional accuracyof several tens of μm or less. Even if such a technique becomesavailable, it is a piece-by-piece technique but does not allow a batchtechnique, which provides no mass productivity causing increase in cost.

For this reason, the optoelectronic wiring board according to theembodiment of the present invention is configured as follows.

The optoelectronic wiring board according to the embodiment of thepresent invention includes: a rigid section in which a laminate of aconductive circuit and an insulating layer is formed on both sides of asubstrate; a flexible flex section; a flex rigid substrate sectionprovided with an electric wiring; and an optical waveguide having an endface substantially perpendicular to an optical path, the end face beingarranged facing an optical element mounting region provided on the rigidsection, and the optical waveguide which bends together with the flexsection is fixed on the rigid section.

Furthermore, the optoelectronic wiring board according to the embodimentof the present invention is characterized in that a condenser lens isprovided on an end face of the optical waveguide, in the above discussedembodiment of the invention.

According to the optoelectronic wiring board according to the embodimentof the present invention having such a configuration, the optical wiringbending together with the flex section is fixed on the rigid section andthe conductive circuit is formed in the rigid section, so that, like theabove-mentioned embodiment of the fundamental invention, a conductivecircuit can be formed in a portion where so high-speed transmission isnot required and an electric wiring is sufficient, while only a linewhich needs high-speed transmission can be an optical wiring. As aresult, considerable increase in amount of information to be processedand increase in speed of information processing can be achieved withoutincreasing the size of the wiring board.

In addition, according to the optoelectronic wiring board according tothe embodiment of the present invention, the optical wiring having anend face substantially perpendicular to an optical path is fixed on therigid section and the end face thereof is arranged facing the opticalelement mounting region on the rigid section so that the end face of theoptical wiring can be optically coupled with the optical elementdirectly without using an optical path changer.

As a result, the configuration of the flex rigid substrate section whichis a main portion can be simplified, so that the optoelectronic wiringboard can be manufactured at low cost by forming the flex rigidsubstrate section using an existing plane process and combining it withthe optical wiring. If the optical wiring is an optical waveguide, theprocess becomes easier.

Furthermore, in the embodiment of the present invention, when acondenser lens is provided on the end face of the optical wiring, anoptical signal can be transmitted to a desired region with morereliability, and the requirement for accuracies of mounting positions ofoptical elements such as a light-emitting element and a light-receivingelement can be thus mitigated, and thus, the cost of mounting componentscan be reduced.

Preferred embodiments of the optoelectronic wiring board according tothe embodiment of the present invention will be described below withreference to the figures. However, the present invention is not limitedto the embodiments shown in the figures. In this connection, concreteexamples using an optical waveguide as an optical wiring will bedescribed below.

FIG. 10A is a cross-sectional view schematically showing an embodimentof the optoelectronic wiring board of the present invention.

As shown in FIG. 10A, similar to the above-mentioned embodiment of thefundamental invention, an optoelectronic wiring board 1 of thisembodiment is composed of a pair of rigid sections 50 a and 50 c and aflex section 50 b integrated with each other, having a flex rigidsubstrate section 2 and an optical waveguide 34.

The flex rigid substrate section 2 has a common flexible substrate 10 inwhich a conductive circuit 4 and a cover lay 5 are formed in this orderon a base film 10 a.

Furthermore, a pair of rigid substrate sections 1 a and 1 c is laminatedin regions at both ends of the flexible substrate 10, and thereby therigid substrate sections 1 a and 1 c and the flexible substrate 10 areintegrated with each other.

The rigid substrate sections 1 a and 1 c are constituted by multilayerwiring substrates in which insulating layers and conductive circuits(for example, insulating layers 6 and 11 and conductive circuits 9) arelaminated on both sides of the flexible substrate 10. In the outmostlayers of the multilayer wiring substrates, conductive circuits 17 and18 are formed.

These conductive circuits 17 and 18 are connected with each other viathrough-hole sections 22. Each of the through-hole sections 22 is filledwith resin composition 23 made of resin similar to that of theembodiment of the fundamental invention described above.

Solder resist layers 19 and 20 are formed in predetermined regions ofthe outermost layers of the rigid substrate sections 1 a and 1 c.

In the case of this embodiment, a connection terminal portion 17 a onthe outermost layer at one side of each of the rigid substrate sections1 a and 1 c are exposed. In this region optical element mounting regions2 a and 2 c are formed.

In addition, according to the embodiment of the present invention, theoptical waveguide 34 is fixed on each of the rigid substrate sections 1a and 1 c.

In the case of this embodiment, the optical waveguide 34 is glued andfixed on solder resist 19 on at least one side, particularly a side onwhich an optical element mounting region 2 a, 2 c is provided, of eachof the rigid substrate sections 1 a and 1 c by pressing the opticalwaveguide 34 with adhesive prepreg 21 between the solder resist 19 andthe optical waveguide 34.

FIG. 10B is a cross-sectional view schematically showing anotherembodiment of the optoelectronic wiring board according to theembodiment of the present invention. This embodiment has the samestructure as that in FIG. 10A except that the flexible substrate 10 isdisposed with partially interposed prepreg 6 a at the flexible substrateside of the rigid substrate section 1 a, 1 c.

The optical waveguide 34 used in the embodiment of the present inventionhas a basic configuration similar to that of the embodiment of thefundamental invention described above, and includes film-like upper andlower clad layers 31 and 33, and a core layer 32, and these layers areflexible. Because of this, the optical waveguide 34 bends together withthe flexible substrate 10 in the flex section 50 b.

On the other hand, in the embodiment of the present invention, theoptical waveguide 34 is not provided with any optical path changer suchas a mirror for changing an optical path, and is configured such thatoptical signals are input and output from both end faces (for example,light-emitting side end face 35 a, light-receiving side end face 35 c)thereof.

Specifically, both end faces 35 a and 35 c of the optical waveguide 34are formed so as to be substantially perpendicular to the optical pathof transmitting light.

Both end portions of the optical waveguide 34 are disposed and fixed onthe rigid substrate sections 1 a and 1 c, respectively, so that both endfaces 35 a and 35 c of the optical waveguide 34 face the optical elementmounting regions 2 a and 2 c on the rigid sections 50 a and 50 c,respectively.

In the embodiment of the present invention, it is desirable but notlimited in particular that the optical waveguide 34 is fixed in such amanner that the end faces 35 of the optical waveguide 34 aresubstantially perpendicular to the substrate surface direction of therigid substrate sections 1 a and 1 c, that is, in such a manner thatlight is input and output in parallel with the substrate surfacedirection of the rigid substrate sections 1 a and 1 c, in view ofaccuracy of input and output of light from and to optical elements, andeasiness of manufacture.

FIG. 11 is a cross-sectional view schematically showing anotherembodiment of the optoelectronic wiring board according to theembodiment of the present invention.

In the embodiment of the present invention, as shown in FIG. 11, acondenser lens 37 may be provided on each of the end faces 35 of theoptical waveguide 34. The condenser lens 37 may be provided on each ofthe end faces 35 a and 35 c of the optical waveguide 34, or only oneither of them.

As such a condenser lens 37, a microlens described above may be used. Inthis case, the microlens can be provided directly on the end face 35 ofthe optical waveguide 34 or via optical adhesive.

Next, the optical communication device and the method of manufacturingthe same according to the embodiment of the present invention will bedescribed.

In this specification, the optical communication device is assumed thatan optoelectronic wiring board on which optical elements are mounted ismounted on another board such as a mother board, a daughter board, abackplane board, or the like. The optoelectronic wiring board may bemounted on another board by any method such as solder ball mounting,soldering, wire bonding, lead frame mounting, TAB mounting, socketmounting, or the like.

In this connection, concrete figure and description of mounting theoptoelectronic wiring board on another board will be omitted.

The optical communication device according to the embodiment of thepresent invention includes: a rigid section in which a laminate of aconductive circuit and an insulating layer is formed on both sides of asubstrate; a flexible flex section; an optical element; a flex rigidsubstrate section provided with an electric wiring; and an opticalwaveguide having an end face substantially perpendicular to an opticalpath, the end face being arranged facing an optical element mountingregion provided on the rigid section, and the optical waveguide thatbends together with the flex section, being fixed on the rigid section.

Furthermore, the optical communication device according to theembodiment of the present invention is characterized in that a condenserlens is provided on the end face of the optical wiring, in the aboveembodiment of the invention.

Furthermore, the optical communication device according to theembodiment of the present invention is characterized in that the opticalelement is mounted on a submount substrate which is mounted on the rigidsection in a standing state, and the optical functional portion of theoptical element is optically coupled with the end face of the opticalwaveguide, in the above embodiment of the invention.

According to the optical communication device according to theembodiment of the present invention having such a configuration, theoptical wiring bending together with the flex section is fixed on therigid section and the conductive circuit is formed in the rigid section,so that, like the embodiment of the fundamental invention, a conductivecircuit can be formed in a portion where so high-speed transmission isnot required and an electric wiring is sufficient, while only a linewhich needs high-speed transmission can be an optical wiring. As aresult, considerable increase in amount of information to be processedand increase in speed of information processing can be achieved withoutincreasing the size of the wiring board.

In addition, according to the optical communication device according tothe embodiment of the present invention, the optical wiring having anend face substantially perpendicular to an optical path is fixed on therigid section and the end face thereof is arranged facing the opticalelement mounting region on the rigid section, so that the end face ofthe optical wiring can be optically coupled with the optical elementdirectly without using an optical path changer.

As a result, the configuration of the flex rigid substrate section whichis a main portion can be simplified, so that the optoelectronic wiringboard can be manufactured at low cost by forming the flex rigidsubstrate section using an existing plane process and combining it withthe optical wiring. When the optical wiring is an optical waveguide, theoptical communication device can be manufactured easily at lower cost.

In addition, in the embodiment of the present invention, if a condenserlens is provided on the end face of the optical wiring, an opticalsignal can be transmitted to a desired region with more reliability, andthe requirement for accuracies of mounting positions of optical elementssuch as a light-emitting element and a light-receiving element can bethus mitigated, so that the cost of mounting components can be reduced.

In addition, in the embodiment of the present invention, when theoptical element is mounted on a submount substrate which is mounted onthe rigid section in a standing state, and the optical functionalportion of the optical element is optically coupled with the end face ofthe optical wiring, the requirement for accuracies of mounting positionsof optical elements such as a light-emitting element and alight-receiving element can be mitigated, so that the cost of mountingcomponents can be reduced. When the optical wiring is an opticalwaveguide, the accuracies of mounting positions can be matched moreeasily.

FIGS. 12A and 12B show the configuration of an embodiment of the opticalcommunication device of the present invention.

An optical communication device 1A shown in FIG. 12A is configured usingthe optoelectronic wiring board 1 described above. Hereinafter,corresponding portions will be attached with common reference numerals,and detail description thereof will be omitted.

In the optical communication device 1A of this embodiment, opticalelements are respectively mounted on the optical element mountingregions 2 a and 2 c on the rigid sections 50 a and 50 c of theoptoelectronic wiring board 1 described above.

In the embodiment of the present invention, the optical elements includeoptical elements such as a light-receiving element and a light-emittingelement described above.

In particular, in the embodiment shown in FIG. 12A, a light-emittingelement (for example, a VCSEL, a PD, or the like) 41 a mounted on asubmount substrate 40 is provided in the optical element mounting region2 a of one rigid section 50 a.

Here, the submount substrate 40 is mounted on a rigid section 50 a in astanding state, and the optical functional portion (not shown) of thelight-emitting element 41 a is arranged facing the end face 35 a of theoptical waveguide 34. Because of this, the optical functional portion ofthe light-emitting element 41 a and the end face 35 a of the opticalwaveguide 34 will be optically coupled with each other.

Furthermore, on the optical element mounting region 2 a, a firstelectronic component (for example, a driving IC chip) 43 a mounted onthe substrate by wire bonding 49 is connected with the light-emittingelement 41 a through bonding wires 44 and 42.

A portion including the light-emitting element 41 a, the firstelectronic component 43 a, and the end face 35 a of the opticalwaveguide 34 is sealed by a sealing portion 45 made of sealing resintransparent to transmission light.

In addition, in this embodiment, a light-receiving element 41 c mountedon a submount substrate 40 is provided in the optical element mountingregion 2 c of the other rigid section 50 c.

The light-receiving element 41 c is mounted on the rigid section 50 c ina state that the submount substrate 40 stands up, and the opticalfunctional portion (not shown) of the light-receiving element 41 c isarranged facing the end face 35 c of the optical waveguide 34. Becauseof this, the optical functional portion of the light-receiving element41 c and the end face 35 c of the optical waveguide 34 will be opticallycoupled with each other.

Furthermore, on the optical element mounting region 2 c, a secondelectronic component (for example, an amplifying IC chip) 43 c mountedon the substrate by wire bonding 49 is connected with thelight-receiving element 41 c through bonding wires 44 and 42.

A portion including the light-receiving element 41 c, the secondelectronic component 43 c, and the end face 35 c of the opticalwaveguide 34 is sealed by a sealing portion 45 transparent totransmission light.

FIG. 12B is a cross-sectional view schematically showing anotherembodiment of the optical communication device according to theembodiment of the present invention.

Also in the optical communication device according to the embodiment ofthe present invention, as shown in FIG. 12B, a condenser lens 37 may beprovided on each of the end faces 35 of the optical waveguide 34. Inthis case, the condenser lens 37 may be provided on each of the endfaces 35 a and 35 c of the optical waveguide 34, or only on either ofthem.

As such a condenser lens 37, the microlens described above may be used.In this case, the microlens may be provided on an end face 35 of theoptical waveguide 34 directly or via optical adhesive.

FIG. 13 is a cross-sectional view schematically showing anotherembodiment of the optical communication device according to theembodiment of the present invention.

In an optical communication device 1B of this embodiment shown in FIG.13, a light-emitting element (for example, an end face light-emittingelement, a waveguide type PD, or the like) 48 a is directly mounted onthe optical element mounting region 2 a of one rigid section 50 a, andthe optical functional portion (not shown) thereof is arranged facingthe end face 35 c of the optical waveguide 34. Because of this, theoptical functional portion of the light-emitting element 48 a and theend face 35 a of the optical waveguide 34 are optically coupled witheach other.

Furthermore, on the optical element mounting region 2 a, a firstelectronic component (for example, a driving IC chip) 43 a mounted onthe substrate by wire bonding 49 is connected with the light-emittingelement 48 a through a bonding wire 44.

A light-receiving element 48 c is directly mounted on the opticalelement mounting region 2 c of the other of the rigid sections 50 c, andthe optical functional portion (not shown) of the light-receivingelement 48 c faces the end face 35 c of the optical waveguide 34.Because of this, the optical functional portion of the light-receivingelement 48 c and the end face 35 a of the optical waveguide 34 isoptically coupled.

Furthermore, on the optical element mounting region 2 c, a secondelectronic component (for example, an amplifying IC chip) 43 c mountedon the substrate by wire bonding 49 is connected with thelight-receiving element 48 c through a bonding wire 44.

Next, examples of a method of manufacturing the optoelectronic wiringboard and optical communication device according to the embodiment ofthe present invention will be described.

FIGS. 14 to 19 are process diagrams showing an example of a method ofmanufacturing the optoelectronic wiring board according to theembodiment of the present invention.

In this example, as shown in FIG. 14A, a flexible substrate in which acopper foil 3 is laminated on one side of a flexible base film 10 a isprepared.

As the base film 10 a, a base film similar to that of the embodiment ofthe fundamental invention described above may be used. For example, anepoxy resin substrate or a substrate made of bismaleimide-triazine (BT)resin may be used.

Furthermore, as the base film 10 a, a base film made of liquid crystalpolymer may also be used. The film made of liquid crystal polymer has ahigh strength and a low expansion coefficient, and is thus suitable forhigh-speed electric transmission.

Next, as shown in FIG. 14B, conductive circuits 4 are formed on one sideof the base film 10 a by forming a resist which is not shown in thefigure and etching it using a publicly known photolithography method.

Next, as shown in FIG. 14C, a cover lay 5 for protection is adhered onthe whole of the conductive circuit 4 side surface of the substrate toobtain an intended flexible substrate 10.

Next, as shown in FIG. 15A, rigid substrates 8 corresponding to thesizes of the rigid sections 50 a and 50 c, respectively, are prepared byperforming router processing for an adhesive film with a copper foil inwhich the copper foil 7 is laminated on one side of prepreg 6.

Next, as shown in FIG. 15B, each rigid substrate 8 is opposed to thebase film 10 a of the flexible substrate 10 and are aligned with theflexible substrate 10 using, for example, alignment marks. After that,they are pressed by applying heat and pressure in order to integratethem.

At that time, they are laminated while being aligned in predeterminedpositions by a pin lamination method or a mass lamination method and areintegrated by being pressed. When they are laminated by a pin laminationmethod, guide holes are previously provided in each of the members.

Then, conductive circuits 9 are formed on the rigid substrates 8 asshown in FIG. 15C by forming resist which is not shown in the figure onthe copper foils 7 of the rigid substrates 8 and etching them.

On the other hand, as shown in FIG. 16A, a adhesive film having a copperfoil in which a copper foil 12 is laminated to one side of a prepreg 11,and an adhesive film with a copper foil in which a copper foil 15 islaminated to one side of a prepreg 14 are prepared. Then, routerprocessing is performed for these films to prepare rigid substrates 13and 16 corresponding to the sizes of the rigid sections 50 a and 50 c.

Then, as shown in FIG. 16B, the rigid substrates 13 and the rigidsubstrates 16 are opposed to the cover lay 5 of the flexible substrate10 and the rigid substrates 8, respectively, from both sides of theflexible substrate 10, and are aligned with the flexible substrate 10.After that, they are pressed to be integrated.

Next, as shown in FIG. 16C, through-hole sections 22 penetrating thewhole of the rigid substrate sections 1 a and 1 c are formed.

In this case, through-holes (not shown) penetrating the whole of therigid substrate sections 1 a and 1 c are formed by, for example, drillprocessing, and to the wall surfaces of the through-holes, treatment bypermanganic acid solution and desmear treatment such as plasmatreatment, corona treatment, or the like, for example, are given.

After that, electroless copper plating and electrolytic copper platingare given to the inner walls of the through-holes to form conductivelayers.

Next, blackening treatment of the inner walls of the through-holes isperformed using predetermined blackening treatment liquid. After that,resin composition 23 described above is filled inside the through-holes,and the copper foils 12 and 15 of the outermost layers of the rigidsubstrate sections 1 a and 1 c are polished.

After that, resist not shown in the figure is formed on the copper foils12 and 15 of the outermost layers of the rigid substrate sections 1 aand 1 c, and then, etching is performed to form conductive circuits 17and 18 on the outermost layers of each of the rigid substrate sections 1a and 1 c as shown in FIG. 17A.

In addition, as shown in FIG. 17B, solder resist layers 19 and 20 areformed in predetermined regions of the outermost layers of the rigidsubstrate sections 1 a and 1 c.

The solder resist layers 19 and 20 can be formed in such a way thatuncured solder resist composition is applied and then curing treatmentis given, or films made of the same uncured solder resist compositionare adhered by pressure and then curing treatment is given as necessary.

By such treatment, a connection terminal portion 17 a on the outermostlayer on one side of each of the rigid substrate sections 1 a and 1 c isexposed. As a result, flex rigid substrate sections 2 in which opticalelement mounting regions 2 a and 2 c are formed in these regions areobtained.

On the other hand, in the embodiment the present invention, an opticalwaveguide can be formed by an ordinary method.

That is, an optical waveguide is formed on a base substrate such as aglass substrate by below-mentioned methods, and then an opticalwaveguide film can be formed by peeling the optical waveguide byimmersion in 3% hydrofluoric acid solution or the like.

Specifically, a method using reactive ion etching, an exposure anddevelopment method, a metal mold forming method, a resist formingmethod, a combination thereof, or the like may be used.

The method using reactive ion etching is able to form an opticalwaveguide having excellent size reliability, and is also excellent forreproducibility.

The exposure and development method can be suitably used whenmass-producing an optical waveguide because of a small number ofprocesses, and does not easily generate a stress on an optical waveguidebecause of a small number of heating processes.

The metal mold forming method can be suitably used when mass-producingan optical waveguide, is able to form an optical waveguide excellent insize reliability, and is also excellent in reproducibility.

The resist forming method can be suitably used when mass-producing anoptical waveguide and is able to form an optical waveguide excellent insize reliability. This method is also excellent in reproducibility.

An optical waveguide may be formed by a photobleaching method, forexample, which prepares, only clad purpose resin composition and forms acore by changing the refractive index of the clad purpose resincomposition by a single-pulse laser such as a femtosecond laser orexposure.

FIGS. 18A to 18D show an example of the manufacturing process of anoptical waveguide according to the embodiment of the present invention.

In this process, at first, a dry film for a lower clad layer 31 isprovided on a substrate 30 capable of being peeled as shown in FIG. 18A,and a dry film for a core layer 32 is laminated on the dry film as shownin FIG. 18B.

Furthermore, a dry film for an upper clad layer 33 is laminated on thefilm as shown in FIG. 18C.

Router processing is performed for an optical waveguide formed like thisto obtain an optical waveguide 34 having predetermined length as shownin FIG. 18D. On both ends thereof, end faces 35 (35 a, 35 c) which aresubstantially perpendicular to an optical path are formed.

After that, prepregs 21 formed in a predetermined size by routerprocessing are prepared as shown in FIG. 19A, and the optical waveguide34 is aligned together with the prepregs 21 onto the solder resistlayers 19 of the rigid substrate sections 1 a and 1 c, and these arepressed to be integrated.

Thereby, an intended optoelectronic wiring board 1 is obtained.

FIGS. 20A and 20B are process diagrams showing an example of amanufacturing process of the optical communication device according tothe embodiment of the present invention.

The optical communication device according to the embodiment of thepresent invention is obtained by mounting optical elements on theoptical element mounting regions 2 a and 2 c on the rigid sections 50 aand 50 c of the above-described optoelectronic wiring board 1,respectively.

For example, when an embodiment shown in FIG. 20A is taken as anexample, in the optical element mounting region 2 a of one rigidsubstrate section 1 a, a submount substrate 40 on which a light-emittingelement 41 a is provided is mounted on the rigid section 50 a in astanding state so that the optical functional portion of thelight-emitting element 41 a is arranged facing the end face 35 a of theoptical waveguide 34.

Furthermore, a first electronic component 43 a is mounted on the opticalelement mounting region 2 a. The first electronic component 43 a isconnected to the connection terminal portion 17 a by wire bonding 49,and is connected to the light-emitting element 41 a through bondingwires 44 and 42.

In the optical element mounting region 2 c of the other rigid section 50c, a submount substrate 40 on which a light-receiving element 41 c isprovided is mounted on the rigid substrate section 1 c in a standingstate so that the optical functional portion of the light-receivingelement 41 c is arranged facing the end face 35 c of the opticalwaveguide 34.

Furthermore, a second electronic component 43 c is mounted on theoptical element mounting region 2 c. The second electronic component 43c is connected to the connection terminal portion 17 c by wire bonding49, and is connected to the light-receiving element 41 c through wirebondings 44 and 42.

After that, as shown in FIG. 20B, a portion including the light-emittingelement 41 a, the first electronic component 43 a, and the end face 35 aof the optical waveguide 34 is sealed by sealing resin (sealing portion45) transparent to transmission light, and a portion including thelight-receiving element 41 c, the second electronic component 43 c, andthe end face 35 c of the optical waveguide 34 is similarly sealed bysealing resin (sealing portion 45) transparent to transmission light.

As a result, an intended optical communication device 1A is obtained.

FIG. 21 is an enlarged cross-sectional view showing the main part ofstill another embodiment of the optical communication device accordingto the embodiment of the present invention.

As shown in FIG. 21, in this embodiment, a coupling optical waveguide 47is provided between the end face 35 of the optical waveguide 34 and theoptical functional portion 46 of the optical element 41, and the opticalwaveguide 34 is optically coupled with the optical element 41 throughthe coupling optical waveguide 47.

The coupling optical waveguide 47 serves as a core layer, and thesealing portion 45 serves as a clad layer. For this reason, it ispreferable that the refractive index of the coupling optical waveguide47 be larger than that of the sealing portion 45. According to such aconfiguration, at optical transmission, light can be trapped in the corelayer so as not to leak to the sealing resin side, so that the lightpropagation loss can be reduced.

The coupling optical waveguide 47 is an optical waveguide provided inclose contact with the end face 35 of the core layer 32 of the opticalwaveguide 34 and the optical functional portion 46 of the opticalelement 41, and can use a self-formed optical waveguide obtained by, forexample, a method described in Japanese Patent Application Laid-open No.2003-14972.

A formation principle of this self-formed optical waveguide is toarrange photosensitive resin so as to wrap the tip of the light-outgoingportion of an optical wiring (or light-emitting element), and a corelayer corresponding to an optical path is formed by irradiating light tothe photosensitive resin through the optical wiring (or light-emittingelement), thereby obtaining an optical waveguide.

In the embodiment of the present invention, the coupling opticalwaveguide can be formed by this self-formation method when the opticalelements and the like and the optical waveguide are sealed with resin.

Specifically, the coupling optical waveguide is formed by, for example,mixing photosensitive resin for self core formation in the sealing resinand irradiating light to resin between the core end face of an opticalwave guide and the optical functional portion of an optical element whenresin sealing is performed.

Such a resin for self core formation can use photosensitive resin, forexample, of which a refractive index is larger after curing than thatbefore curing and is become larger than that of sealing resin, and also,can be polymerized with intensity light lower than that for the sealingresin.

As described above, when an optical waveguide is formed, as describedabove, using photosensitive composition including two kinds ofphotosensitive resins which are different in the intensity of light forpolymerization reaction proceeds, resins in which polymerizationreaction proceeding through polymerization reaction mechanisms differentfrom each other can be selected as the resin for self core formation andthe sealing resin.

In other words, radical polymerization photosensitive resin in whichpolymerization proceeds with sequential polymerization reactions byradicals, typified by acrylic resin, and cationic polymerizationphotosensitive resin in which polymerization proceeds via ion pairs,typified by epoxy resin, can be selected. When these resins areselected, polymerization reaction in radical polymerizationphotosensitive resin proceeds more rapidly than that in cationicpolymerization photosensitive resin, so that only acrylic resin isselectively polymerized by low intensity light.

FIGS. 22A and 22B are cross-sectional views showing examples of placeswhere coupling optical waveguides are formed in the embodiment of thepresent invention.

A coupling optical waveguide described above may be provided on both oreither one of the light-emitting side and the light-receiving side. Fromthe viewpoint of minimizing the transmission loss of an optical signal,it is preferable to provide a coupling optical waveguide on both of thelight-emitting side and the light-receiving side. When providing acoupling optical waveguide on only one of the light-emitting side andthe light-receiving side, it is preferable to provide the couplingoptical waveguide on the light-receiving side from the viewpoint ofreducing the transmission loss of an optical signal.

In the example shown in FIG. 22A, coupling optical waveguides 47 a and47 c are provided between the light-emitting side end face 35 a of theoptical waveguide 34 and the light-emitting element 41 a, and betweenthe light-receiving side end face 35 c of the optical waveguide 34 andthe light-receiving element 41 c, respectively, at the optical elementmounting regions.

In the example shown in FIG. 22B, a coupling optical waveguide 47 c isprovided only between the light-receiving side end face 35 c of theoptical waveguide 34 and the light-receiving portion 46 c of thelight-receiving element 41 c.

FIGS. 23A to 23C show schematically illustrations of an example of amethod of forming a coupling optical waveguide in the embodiment of thepresent invention.

In the example shown in FIG. 23A, in the state that sealing resin 45 ain which resin for self core formation is mixed is provided, light isirradiated to resin between the end face 35 of the optical waveguide 34and the optical functional portion 46 of the optical element 41.

For example, light from an UV light source 61 is irradiated to theoptical functional portion 46 of the optical element 41 through anoptical fiber 60 and the optical waveguide 34.

As the light to be irradiated, low intensity light, that is, lighthaving a intensity which is able to polymerize the resin for self coreformation but is not substantially able to polymerize the sealing resinis used.

As a result, only the higher-photosensitive resin for self coreformation among the photosensitive composition selectively starts topolymerize. When only the resin for self core formation of thephotosensitive composition including the resin for self core formationand the sealing resin starts to polymerize, the uncured sealing resin isremoved from the curing resin for self core formation because theuncured sealing resin keeps liquidity.

Furthermore, the refractive index of the self-formed core layer islarger than that of the uncured sealing resin, so that light which isirradiated through the optical waveguide 34 is intensively irradiated toa tip end of the formed core layer while being trapped in the formedcore layer.

As a result, the resin for self core formation is cured on a priority bylight irradiated from the end face 35 of the optical waveguide 34according to the path of the light as shown in FIG. 23B, a self corelayer 36 corresponding to the path of the light is formed, and the selfcore layer 36 is surrounded by the uncured photosensitive composition(sealing resin and the uncured resin for self core formation).

By growth of the self core layer 36, a coupling optical waveguide 47 isformed between the end face 35 of the optical waveguide 34 and theoptical functional portion 46 of the optical element 41 as shown in FIG.23 C.

After that, for example, light from a light source not shown in thefigure is irradiated to the whole of the uncured sealing resin 45 a, andthen the output of the light source is increased to irradiate lighthaving intensity capable of polymerizing the sealing resin. As a result,the sealing resin and the uncured resin for self core formation is curedto form a sealing portion 45 surrounding the optical element 41, thecoupling optical waveguide 47, and the tip end portion of the opticalwaveguide 34.

On the other hand, in the embodiment of the present invention, as theresin for self formation, photosensitive resin may be used which has arefractive index after curing larger than that before curing and largerthan that of sealing resin, while it can be polymerized by irradiatinglight having a wavelength different from that for the sealing resin.

In this case, for example, light from the UV light source 61 isirradiated to the optical functional portion 46 of the optical element41 through the optical fiber 60 and the optical waveguide 34 (opticalwiring) to form a coupling optical waveguide 47 between the end face 35of the core layer 32 of the optical waveguide 34 and the opticalfunctional portion 46 of the optical element 41. After that, thewavelength of the light to be irradiated is changed and the changedlight is irradiated to the whole of the uncured sealing resin 45 a inorder to cure the uncured sealing resin surrounding the optical element41, the coupling optical waveguide 47, and the tip end portion of theoptical waveguide 34, thereby, the sealing portion 45 is formed.

In the embodiment of the present invention, an optical waveguide whichis excellent in connectivity with the optical element and is excellentin stability because the whole of the system is solidified can be formedby using such a formation method.

In the embodiment of the present invention, the mixing ratio of theresin for self core formation mixed in the sealing resin is not limitedin particular.

On the other hand, in the embodiment of the case of the presentinvention, the sealing portion can be formed also in such a manner thatafter self-forming a coupling optical waveguide as described above,uncured photosensitive composition and the like around the couplingoptical waveguide are removed, and then the optical element, thecoupling optical waveguide, and the tip end portion of the opticalwaveguide are covered with sealing resin having a refractive index aftercuring smaller than that of the self core layer, and the uncured resinis cured by irradiating light to or heating the whole of the sealingresin to form the sealing portion.

However, from the viewpoint of easiness of handling after self-formationof a coupling optical waveguide, it is preferable to adopt a method ofmixing resin for self core formation having a different refractive indexin the sealing resin.

In the resin for self core formation, particles such as resin particles,inorganic particles, metal particles, or the like may also be included.By forming an optical waveguide using photosensitive composition or thelike including such particles, the coefficient of thermal expansion ofthe optical wiring can be matched with that of the optical waveguide.

Detail description about the operation and effect in the case thatparticles are contained in the resin for self core formation is omittedhere because description about the operation and effect in the case thatparticles are contained in the optical waveguide according to theembodiment of the present invention or the like has already beenprovided.

Such resin particles include ones made of, for example, thermosettingresin, thermoplastic resin, photosensitive resin, thermosetting resinpart of which is made photosensitive, resin complexes of thermosettingresin and thermoplastic resin, complexes of photosensitive resin andthermoplastic resin, or the like.

Specifically, such resin particles include ones made of, for example,thermosetting resin such as epoxy resin, phenolic resin, polyimideresin, bismaleimide resin, polyphenylene resin, polyolefin resin,fluororesin or the like; resin made by causing methacrylic acid, acrylicacid, or the like to react with the heat curing group (for example, anepoxy group in epoxy resin) of the thermosetting resin and adding anacrylic group to the heat curing group; thermoplastic resin such asphenoxy resin, polyeter sulfone (PES), poly sulfone (PSF), polyphenylenesulfone (PPS), polyphenylene sulfide (PPES), poly phenyl ether (PPE),polyeter imide (PI), or the like; photosensitive resin such as acrylicacid resin; or the like.

Furthermore, the resin particles may use ones made of resin complex ofsuch thermosetting resin and thermoplastic resin, or resin complex ofthe acrylic group added resin or the photosensitive resin and thethermoplastic resin. Furthermore, the resin particles may be made ofrubber.

Furthermore, the inorganic particles include ones made of, for example,aluminum compound such as alumina or aluminium hydroxide, calciumcompound such as calcium carbonate or calcium hydroxide, potassiumcompound such as potassium carbonate, magnesium compound such asmagnesia, dolomite, or magnesium carbonate basic, silicon compound suchas silica or zeolite, or the like. Furthermore, the inorganic particlesmay use ones made of phosphorus or phosphorus compound.

The metal particles include ones made of, for example, gold, silver,copper, palladium, nickel, platinum, iron, zinc, lead, aluminum,magnesium, calcium, or the like. These resin particles, inorganicparticles, and metal particles may be used singly or in combination oftwo or more kinds of them.

Furthermore, shapes of the particles are not limited in particular, andinclude, for example, spheres, ellipsoids, crush shapes, polyhedrons,and the like. In these shapes, spheres or ellipsoids are preferablebecause particles of spheres or ellipsoids have no edge so that a crackor the like is hard to occur to the optical waveguide.

Furthermore, it is desirable that the particle diameters of theparticles be shorter than the communication wavelength, because if theparticle diameters are longer than the communication wavelength,transmittance of an optical signal may be interfered. In thisspecification, the particle diameter of a particle is the length of thelongest portion of the particle.

When the photosensitive composition or the like contains particles, adesirable mixed amount thereof after curing is between 10 weight % and80 weight %, and a more desirable one is between 20 weight % and 70weight %. Because if the mixed amount of particles is less than 10weight %, the effect of mixing particles is not almost obtained, whileif the mixed amount of particles is more than 80 weight %, transmissionof an optical signal may be inhibited.

Furthermore, the photosensitive composition or the like is cured byirradiating light to become a core layer having a refractive index of aspecific range. Thus, in the formation method according to theembodiment of the present invention, photosensitive composition or thelike which becomes a core layer having a refractive index in the aboverange may be selected and used. However, photosensitive composition orthe like which becomes a core layer having a refractive index outsidethe above range may also be used by adjusting the refractive index.Furthermore, when the refractive index of photosensitive composition orthe like is adjusted, it is desirable that the refractive index beadjusted in such a manner that the refractive index of a core layerbefore or after curing falls within the above range.

In the above example, light is irradiated to the resin for self coreformation from the optical waveguide. However, when a UV VCSEL or a UVLED (output light wavelength λ=365 nm), for example, is used as thelight-emitting element, the coupling optical waveguide may beself-formed by irradiating light to the resin for self core formationfrom the light-emitting element, or from both of the light-emittingelement and the optical waveguide.

FIGS. 24A to 24C schematically illustrate another example of a method offorming a coupling optical waveguide in the embodiment of the presentinvention, showing a case that light is irradiated from both of thelight-emitting element and the optical waveguide.

As shown in FIGS. 24A to 24C, in this case, light is irradiated from thelight-emitting element 41 a to the optical waveguide 34 and light fromthe UV light source 61 is irradiated toward the light-emitting portion46 a of the light-emitting element 41 a through the optical fiber 60 andthe optical waveguide 34, in order to grow a self core layer 36 betweenthe light-emitting side end face 35 a of the optical waveguide 34 andthe light-emitting portion 46 a of the light-emitting element 41 a toform a coupling optical waveguide 47.

After that, predetermined light is irradiated to the whole of uncuredsealing resin 45 a in order to cure the uncured resin surrounding theoptical element, the core layer, and the tip end portion of the opticalwaveguide 34 to form a sealing portion 45.

As described above, when light is irradiated to the resin for self coreformation from both side of the light-emitting element and the opticalwaveguide, a self core layer can be formed with reliability even if theoptical axis of the light-emitting element is misaligned a little withthat of the optical waveguide, so that there is an advantage that therequirement for accuracies of positions of the light-emitting elementand the optical waveguide can be mitigated.

FIGS. 25A to 25C schematically illustrate another example of a method offorming a coupling optical waveguide in the embodiment of the presentinvention, showing a case that light is irradiated from both side of thelight-emitting element and the optical waveguide to form a couplingoptical waveguide on each of the light-emitting side and thelight-receiving side.

In this case, first, light is irradiated from the light-emitting element41 a to the optical waveguide 34 and light from the UV light source 61is irradiated to the light-emitting portion 46 a of the light-emittingelement 41 a through the optical fiber 60 and the optical waveguide 34in order to form a coupling optical waveguide 47 between thelight-emitting side end face 35 a of the optical waveguide 34 and thelight-emitting portion 46 a of the light-emitting element 41 a, and thenuncured resin is cured to form a sealing portion 45.

Next, a light-receiving element 41 c is mounted, and light from thelight-emitting element 41 a is irradiated to the light-receiving portion46 c of the light-receiving element 41 c through the optical waveguide34 in order to form a coupling optical waveguide 47 between thelight-receiving side end face 35 c of the optical waveguide 34 and thelight-receiving portion 46 c of the light-receiving element 41 c, andthen uncured resin is cured to form a light-receiving side sealingportion 45.

FIGS. 26A to 26C schematically illustrate another example of a method offorming a coupling optical waveguide in the embodiment of the presentinvention, showing a case that light is irradiated only from thelight-emitting element to form a coupling optical waveguide on each ofthe light-emitting side and the light-receiving side.

In this case, first, light is irradiated from the light-emitting element41 a to the optical waveguide 34 in order to form a coupling opticalwaveguide 47 between the light-emitting side end face 35 a of theoptical waveguide 34 and the light-emitting portion 46 a of thelight-emitting element 41 a, and then uncured resin is cured to form asealing portion 45.

Next, a light-receiving element 41 c is mounted, and light from thelight-emitting element 41 a is irradiated to the light-receiving portion46 c of the light-receiving element 41 c through the optical waveguide34 in order to form a coupling optical waveguide 47 between thelight-receiving side end face 35 c of the optical waveguide 34 and thelight-receiving portion 46 c of the light-receiving element 41 c, andthen uncured resin is cured to form a light-receiving side sealingportion 45.

FIGS. 27A to 27C schematically illustrate another example of a method offorming a coupling optical waveguide in the embodiment of the presentinvention, showing a case that light is irradiated from both side of thelight-emitting element and the optical waveguide to form a couplingoptical waveguide only on the light-emitting side.

In this case, light is irradiated from the light-emitting element 41 ato the optical waveguide 34 and light from the UV light source 61 isirradiated to the light-emitting portion 46 a of the light-emittingelement 41 a through the optical fiber 60 and the optical waveguide 34in order to form a coupling optical waveguide 47 between thelight-emitting side end face 35 a of the optical waveguide 34 and thelight-emitting portion 46 a of the light-emitting element 41 a, and thenuncured resin is cured to form a sealing portion 45.

Next, a light-receiving element 41 c is mounted and sealed with resin toform a light-receiving side sealing portion 45.

FIGS. 28A to 28B schematically illustrate another example of a method offorming a coupling optical waveguide in the embodiment of the presentinvention, showing a case that light is irradiated only from thelight-emitting element to form a coupling optical waveguide only on thelight-emitting side.

In this case, light is irradiated from the light-emitting element 41 ato the optical waveguide 34 in order to form a coupling opticalwaveguide 47 between the light-emitting side end face 35 a of theoptical waveguide 34 and the light-emitting portion 46 a of thelight-emitting element 41 a, and then, uncured resin is cured to form asealing portion 45.

Next, a light-receiving element 41 c is mounted and sealed with resin toform a light-receiving side sealing portion 45.

FIGS. 29A and 29B and FIGS. 30A and 30B each schematically illustrateanother example of a method of forming a coupling optical waveguide inthe embodiment of the present invention, the method being applied to acase that a coupling optical waveguide is formed using a givenlight-emitting element other than a UV VCSEL or UV LED described above.

In the example shown in FIGS. 29A and 29B, first, light from the UVlight source 61 is irradiated to the light-emitting portion 46 a of thelight-emitting element 41 a through the optical fiber 60 and the opticalwaveguide 34 in order to form a coupling optical waveguide 47 betweenthe light-emitting side end face 35 a of the optical waveguide 34 andthe light-emitting portion 46 a of the light-emitting element 41 a, andthen, uncured resin is cured to form a sealing portion 45.

Next, a light-receiving element 41 c is mounted and sealed with resin toform a light-receiving side sealing portion 45.

On the other hand, in the example shown in FIGS. 30A and 30B, first,light from the UV light source 61 is irradiated to the light-receivingportion 46 c of the light-receiving element 41 c through the opticalfiber 60 and the optical waveguide 34 in order to form a couplingoptical waveguide 47 between the light-receiving side end face 35 c ofthe optical waveguide 34 and the light-receiving portion 46 c of thelight-receiving element 41 c, and then, uncured resin is cured to form asealing portion 45.

Next, a light-emitting element 41 a is mounted and sealed with resin toform a light-emitting side sealing portion 45.

In the above embodiments, the present invention is described taking anoptical waveguide as an example. However, the present invention is notlimited to this, and an optical fiber sheet may be used instead of anoptical waveguide.

Furthermore, the number of layers of rigid sections is not limited, andthe rigid sections may be integrated with flex sections at any layers.

1. An optoelectronic wiring board comprising: a flex-rigid substrateincluding: a flexible substrate provided with an electric wiring; and apair of rigid sections provided on both sides of the flexible substrate,the pair of rigid sections each comprising a lamination formed of aconductive circuit and an insulating layer; and optical communicationmeans made of a flexible material and having both end facessubstantially perpendicular to its optical path of transmitting light,wherein both end portions of the optical communication means aredisposed and fixed on the rigid sections so that both end faces of theoptical communication means face an optical element mounting regionprovided on the rigid sections of the flex-rigid substrate.
 2. Theoptoelectronic wiring board according to claim 1, the opticalcommunication means being an optical waveguide or an optical fibersheet.
 3. The optoelectronic wiring board according to claim 2, theoptical waveguide being an organic optical waveguide made of polymermaterial.
 4. The optoelectronic wiring board according to claim 1,further comprising a condenser lens provided on at least one of the endfaces of the optical communication means.
 5. The optoelectronic wiringboard according to claim 1, further comprising submount substratesmounted on the rigid sections in a standing state so as to be arrangedfacing the optical communication means.
 6. An optical communicationdevice comprising: a flex-rigid substrate including: a flexiblesubstrate provided with an electric wiring; and a pair of rigid sectionsprovided on both sides of the flexible substrate, the pair of rigidsections each comprising a lamination formed of a conductive circuit andan insulating layer; optical communication means made of a flexiblematerial and having both end faces substantially perpendicular to itsoptical path of transmitting light; and a pair of optical elementshaving their respective optical functional portions that are mounted onthe rigid sections of the flex-rigid substrate, wherein both endportions of the optical communication means are disposed and fixed onthe rigid sections so as to face the optical elements, and a condenserlens is provided on at least one of the end faces of the opticalcommunication means.